CN114616439A - Sensing system using current guided bridge - Google Patents

Abstract

Embodiments described herein relate to a system having a processor and a bridge circuit. The bridge circuit includes a pair of differential voltage sources, a first pair of sensing elements, and a second pair of sensing elements. The first pair of sensing elements generates a pair of measurement signals. The pair of measurement signals are independent of each other and are based on respective sensing elements. The second pair of sensing elements is communicatively coupled to the first pair of sensing elements. The second pair of sense elements define a first divider. The pair of measurement signals is input into a corresponding second sensing element of the second pair of sensing elements. The first divider is configured to output the first output signal to the processor. The first output signal is the first differential signal of the first pair of sensing elements.

Description

Sensing System Using Current Steering Bridge

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to US Patent Application Serial No. 16/670,613, "Sensing Systems Using Current Steering Bridges," filed October 31, 2019, the contents of which are incorporated in their entirety under 35 U.S.C. §119(e) This article.

technical field

The present disclosure relates to electronic circuits and systems, and more particularly, to sensing circuits for detecting changes in fluid, pressure, and/or force.

Background technique

Among the many types of sensors used in automotive applications, the level sensor is one of the simplest in shape and size. For example, other sensors require a float mechanism or a series of switches that toggle when the liquid level rises or falls. The liquid level sensor does not require a float mechanism or a series of small switches, but simply implements a printed pattern of electrodes on a common PCB, so the design and implementation are simple and compact. Capacitive sensors are based on changes in capacitance within a given system, inductive sensors are based on changes in inductance within a given system, and resistive sensors are based on changes in impedance within a given system. As the liquid level in the system changes, the amount of capacitance, inductance and/or resistance increases or decreases.

However, despite their simplicity in design and application, conventional capacitive, inductive and/or resistive liquid level sensors suffer from several problems. For example, traditional capacitive, inductive and/or resistive sensors have a higher noise floor than any other type of implementation due to the very high source impedance of capacitive, inductive and/or resistive sensors, so EMC design is very difficult. Therefore, incoming noise cannot be easily filtered out due to the high source impedance. High source impedance causes the sensor's output to have a high noise level and become unstable. For example, the impedance of a single capacitor, inductor, and/or resistor powered by a DC power source is essentially infinite. Therefore, frequencies are traditionally driven at frequencies in the 10Khz range.

Accordingly, sensors with the versatility to use sensors driven by high RF frequencies, as well as to provide accurate fluid, pressure and/or force level measurements, are desired.

SUMMARY OF THE INVENTION

In one aspect, a system having a processor, a first bridge circuit, and a second bridge circuit is provided. The first bridge circuit is communicatively coupled to the processor. The first bridge circuit has a first pair of differential voltage sources and a first pair of capacitors configured to drive the first bridge circuit. A first pair of capacitors generates a first pair of measurement signals. One capacitor of the first pair of capacitors is positioned in contact with the first measurable medium. The first pair of measurement signals are independent of each other and are based on the outputs of the respective capacitors. The second bridge circuit is communicatively coupled to the processor. The second bridge circuit has a second pair of differential voltage sources and a second pair of capacitors configured to drive the second bridge circuit. A second pair of capacitors generates a second pair of measurement signals. One capacitor of the second pair of capacitors is positioned in contact with the second measurable medium. The second pair of measurement signals are independent of each other and are based on the outputs of the respective capacitors. The first bridge circuit outputs the first output signal to the divider, and the second bridge circuit outputs the second output signal to the divider. The divider generates a ratiometric output signal. The ratio metric output signal is determined by the processor as the ratio of the first output signal to the second output signal.

In another aspect, a system having a processor, a first bridge circuit, and a second bridge circuit is provided. The first bridge circuit is communicatively coupled to the processor. The first bridge circuit has a first pair of differential voltage sources and a first pair of inductors configured to drive the first bridge circuit. The first pair of inductors generates a first pair of measurement signals. One inductor of the first pair of inductors is positioned in contact with the first measurable medium. The first pair of measurement signals are independent of each other and are based on the outputs of the respective inductors. The second bridge circuit is communicatively coupled to the processor. The second bridge circuit has a second pair of differential voltage sources and a second pair of inductors configured to drive the second bridge circuit. The second pair of inductors generates a second pair of measurement signals. One inductor of the second pair of inductors is positioned in contact with the second measurable medium. The second pair of measurement signals are independent of each other and are based on the outputs of the respective inductors. The first bridge circuit outputs the first output signal to the divider, and the second bridge circuit outputs the second output signal to the divider. The divider generates a ratiometric output signal. The ratio metric output signal is determined by the processor as the ratio of the first output signal to the second output signal.

In yet another aspect, a system having a processor, a first bridge circuit, and a second bridge circuit is provided. The first bridge circuit is communicatively coupled to the processor. The first bridge circuit has a first pair of differential voltage sources and a first pair of resistors configured to drive the first bridge circuit. The first pair of resistors generates a first pair of measurement signals. One resistor of the first pair of resistors is positioned in contact with the first measurable medium. The first pair of measurement signals are independent of each other and are based on the outputs of the respective resistors. The second bridge circuit is communicatively coupled to the processor. The second bridge circuit has a second pair of differential voltage sources and a second pair of resistors configured to drive the second bridge circuit. The second pair of resistors generates a second pair of measurement signals. One resistor of the second pair of resistors is positioned in contact with the second measurable medium. The second pair of measurement signals are independent of each other and are based on the outputs of the respective resistors. The first bridge circuit outputs the first output signal to the divider, and the second bridge circuit outputs the second output signal to the divider. The divider generates a ratiometric output signal. The ratio metric output signal is determined by the processor as the ratio of the first output signal to the second output signal.

Description of drawings

Reference will now be made to the accompanying drawings in conjunction with reading the following detailed description, wherein like reference numerals refer to like parts throughout the several views, and wherein:

1A schematically depicts a circuit diagram of a pair of inverting voltage sources implemented by a differential LC oscillator in accordance with one or more embodiments shown and described herein;

FIG. 1B schematically depicts a current steering bridge circuit with a bias voltage with a sensor capacitor connected to an inverting voltage source in accordance with one or more embodiments shown and described herein;

Figure 1C schematically depicts a pair of sine and cosine signal representations derived from a pair of current steering bridge circuits for use in the same manner as inductive in accordance with one or more embodiments shown and described herein. Used with signal processors for sensor applications;

2 schematically depicts a capacitive current steering bridge circuit in accordance with one or more embodiments shown and described herein, wherein the source voltage is equal to zero and the output voltage is indicated to be proportional to the differential capacitance around zero;

Figure 3 schematically depicts the linear ratiometric output of a three-terminal transducer in accordance with one or more embodiments shown and described herein;

Figure 4 schematically depicts the quadrature ratio metric output of a four-terminal transducer in accordance with one or more embodiments shown and described herein;

5A schematically depicts a variable capacitor of a capacitive voltage divider with phase I on a first layer and a phase I on a second layer in accordance with one or more embodiments shown and described herein Q-phases, which are integrated into the associated processor chip for the required quadrature signal generation;

5B schematically depicts the variable capacitor of the capacitive voltage divider of FIG. 5A positioned within a reservoir in accordance with one or more embodiments shown and described herein;

6 is a cross-sectional view of an interdigital electrode capacitor formed with electric field lines to prevent oil immersed in an associated processor from sticking to the capacitor, in accordance with one or more embodiments shown and described herein. between the thicknesses of the plates, thereby increasing the sensing speed and improving the associated response time;

7A is a circuit diagram of an unbalanced capacitor pair with a balanced voltage pair of an inverting voltage source in accordance with one or more embodiments shown and described herein;

7B is a circuit diagram of a balanced capacitor pair with a single control capacitor inserted, and a balanced voltage pair with an inverting voltage source, in accordance with one or more embodiments shown and described herein;

7C is a circuit diagram of a balanced capacitor pair with two control capacitors inserted and a balanced voltage pair with an inverting voltage source in accordance with one or more embodiments shown and described herein;

8 illustrates a sensor layout with a diamond design in accordance with one or more embodiments shown and described herein;

9 illustrates diamond design parameters in accordance with one or more embodiments shown and described herein;

10 illustrates a connector pinout on a sensor in accordance with one or more embodiments shown and described herein;

11 illustrates a circuit layout on a PCB in accordance with one or more embodiments shown and described herein;

12 schematically illustrates an LC inductive sensor with a differential LC oscillator and a Thevenin equivalent circuit in accordance with one or more embodiments shown and described herein;

13 schematically illustrates a current steering bridge circuit having a differential amplifier with a current pool to form a bridge circuit in accordance with one or more embodiments shown and described herein;

FIG. 14A schematically illustrates the pilot bridge circuit of FIG. 13, wherein the impedance is replaced with a bridge impedance element, in accordance with one or more embodiments shown and described herein;

Figure 14B schematically illustrates the Thevenin equivalent current steering bridge circuit of Figure 14A in accordance with one or more embodiments shown and described herein;

15A schematically illustrates a differential impedance current steering bridge circuit with the quarter bridge of FIG. 14A in accordance with one or more embodiments shown and described herein;

15B schematically illustrates a differential impedance current steering bridge circuit with the quarter bridge of FIG. 14A in accordance with one or more embodiments shown and described herein;

16 schematically illustrates a differential capacitive current steering bridge circuit with the quarter bridge of FIG. 14A in accordance with one or more embodiments shown and described herein;

17A schematically illustrates a center-tapped differential inductor current steering bridge circuit with two variable inductors in accordance with one or more embodiments shown and described herein;

17B schematically illustrates a center-tapped, differential inductor current steering bridge circuit with four variable inductors in accordance with one or more embodiments shown and described herein;

17C schematically illustrates a single-bridge differential circuit in accordance with one or more embodiments shown and described herein;

17D schematically illustrates a differential bridge circuit with dual bridges in accordance with one or more embodiments shown and described herein;

Figure 17E schematically illustrates a single bridge ratio metric circuit in accordance with one or more embodiments shown and described herein; and

18 schematically illustrates a ratiometric output of a differential capacitive current steering bridge circuit in accordance with one or more embodiments shown and described herein.

Detailed ways

Embodiments described herein relate to a system having a processor and a bridge circuit. The bridge circuit includes a pair of differential voltage sources, a first pair of sensing elements, and a second pair of sensing elements. The pair of differential voltage sources is configured to drive the first bridge circuit.

The first pair of sensing elements and the second pair of sensing elements may each be configured to generate a pair of measurement signals. The pair of measurement signals are independent of each other and are based on respective sensing elements. The second pair of sensing elements is communicatively coupled to the first pair of sensing elements. The second pair of sense elements define a first divider. The first divider is configured to output the first output signal to the processor. The first output signal is a differential signal.

As will be described further below, the first pair of sensing elements and the second pair of sensing elements are from a combination of a set of capacitors, inductors and resistors. In embodiments in which the first pair of sensing elements generates a pair of measurement signals, the pair of measurement signals is input into a corresponding second sensing element of the second pair of sensing elements. The pair of measurement signals are differential measurements corresponding to the force in contact with the bridge circuit. Differential measurements can be impedance, inductance, or capacitance, or a combination thereof.

In embodiments in which the second pair of sensing elements generates a pair of measurement signals, the pair of measurement signals are independent of each other and are based on the respective second sensing elements. In this embodiment, the pair of measurement signals are differential measurements corresponding to the force in contact with the bridge circuit. Differential measurements can be impedance, inductance, or capacitance, or a combination thereof.

In some embodiments, the bridge circuit is a single bridge for differential output. In other embodiments, the bridge circuit is a dual bridge for ratiometric output. Thus, in a dual bridge embodiment, the bridge circuit may include a third pair of sense elements communicatively coupled to the first pair of sense elements and in parallel with the second pair of sense elements. The third pair of sensing elements is a combination from a set of capacitors, inductors and resistors. The third pair of sensing elements may receive or generate a second pair of measurement signals received or generated by a corresponding third sensing element of the third pair of sensing elements corresponding to the force in contact with the bridge circuit . The third pair of sensing elements defines a second divider. The third pair of sensing elements outputs a second output signal to the divider. A divider divides the first output signal by the second output signal to generate a ratio metric signal.

It will be appreciated that by employing a bridge circuit, the differential signal and/or ratiometric signal is independent of common mode noise from the transducer and circuit. Therefore, separate differential signals can be used, or a ratiometric measure of the differential output can be used simultaneously.

That is, as will be further described, the bridge circuit is configured for differential measurements for maximum information transfer, whereas non-differential measurements include specific and common signals that are not part of the information. In addition, the same sensor configuration is used to measure ratiometric measurements for different media, since all common-mode signals are rejected. Bridge circuits with ratiometric measurements allow not only capacitive sensors to be implemented, but also inductive sensors and resistive sensing within the sensing architecture.

As used herein, the term "communicatively coupled" means that coupled components are capable of exchanging data signals and/or electrical signals with each other, such as, for example, electrical signals via conductive media, electromagnetic signals via air, light via optical waveguides Signals, electrical energy via conductive or non-conductive media, wireless and/or data signals via conductive or non-conductive media, and the like.

In summary, and with reference to the drawings, FIG. 1A generally shows at 10 a circuit diagram of a pair of inverting voltage sources supplying the LC circuit and ultimately to the processor chip, which is then driven at 74 by the The general example reference, and in one variant, includes an inductive sensor chip, which is known to provide advantages over magnetic sensors when applied to numerous vehicle applications including linear/rotary pedal position, fuel level, etc. robustness and longevity. Although not shown, existing current inductive sensors may also include a miniaturized processor chip or PC board with signal processing components provided with inductive signal input functions, such as including support on the transmitter Aluminium rotor on coil and receiver coil arrangement.

In accordance with the teachings of the present invention, a pair of variable capacitors associated with the chip may also include space array plates immersed in a fluid (eg, oil) medium to provide liquid level readings. Circuit 10 in FIG. 1A also depicts a pair of opposing excitation voltage sources at 12 and 14 on opposite sides of capacitor 16 associated with the LC resonator of the inductive sensor drive circuit, see at 18, Its output is supplied as a trace current (typically less than 1 mA) through ammeter 20 for subsequent conversion to a varying voltage output.

Figure IB is a diagram of a current steering bridge circuit with bias voltage (see generally at 22) with a pair of sensor capacitors (see variable capacitor Csen at 24 and capacitor CREF at 26) connected to the inverting phase Voltage sources 12 and 14, whose amplitudes are the same for all drive frequencies (eg, including non-limiting ranges from hundreds of Khz to tens of Mhz). In such an arrangement, the variable capacitor 24 becomes a current source, pumping an amount of excitation current through resistor 30 (see at 28 ), while another capacitor 26 generates excitation current 32 through resistor 34 .

The current-steering bridge circuit structure operates to steer the differentially generated opposite phase current between the capacitors, the resulting sensed current (see at 36 and corresponding to the differential current) appearing as voltage 38 across resistor 36 . FIG. 1C provides a graph of a pair of sine signals 40 and cosine signals 42 derived from a pair of current steering bridge circuits such as shown in FIG. 1B for use with a signal processor chip also suitable for inductive sensor applications.

Figure 2 illustrates the capacitive current steering bridge circuit of Figure IB. As shown further generally at 44, see also at 38', the source voltage set equal to zero indicates that the output voltage is proportional to the differential capacitance 36' at about zero reading.

3 schematically depicts a system 500 including a transducer 502 having three terminals 504a, 504b, 504c communicatively coupled to an inverting voltage source 58, 60. The inverting voltage sources 58 , 60 are configured to drive the first variable capacitor 505 and the second variable capacitor 507 to generate the level output 406 and the reference output 508 . It should be understood that the application is not limited to capacitors, and may be inductors, resistors, and/or combinations thereof. Thus, Figure 3 illustrates a linear ratio metric output 510 with a three-terminal transducer. It will be appreciated that such an arrangement allows for a compact transducer plate. Linear ratio metric output 510 is depicted with respect to graph 512 having ordinate 514 and abscissa 516, where level output 506 and reference output 508 may be graphically illustrated as level output plot 518 and reference output plot 520. Diagram 512 also illustrates level 522 , bottom 526 and zero level point 524 . Bottom 526 may be the bottom of a receptacle or the like.

The zero level point 524 may be the lowest level required to obtain a reading. As shown, the linear ratio metric output 510 is independent of the liquid level 522 . Therefore, by taking the ratio of the two differential outputs (eg, level output 506 and reference output 508 ) as the liquid level 522 changes, the ratiometric output 510 is fluid independent and the bridge circuit eliminates the Common mode noise, as discussed in more detail in this article. It should be understood that the liquid level 522 is for example purposes only, and could also be illustrated in terms of pressure, force, etc., so that there are two differential outputs. For example, in the case of force, the one level output is the measured force when the force is applied, and the reference output is the normal force when no force is applied.

FIG. 4 schematically depicts a system 530 that includes a transducer 532 having four terminals 534a , 534b , 534c , 534d communicatively coupled to inverting voltage sources 58 , 60 . The inverting voltage sources 58 , 60 are configured to drive the first variable capacitor 535 and the second variable capacitor 537 to produce a sine output 536 and a cosine output 538 . It should be understood that the application is not limited to capacitors, and may be inductors, resistors, and/or combinations thereof. Thus, Figure 4 illustrates the quadrature ratio metric output 540 with a four-terminal transducer. It will be appreciated that such an arrangement allows for a compact transducer plate and may require an arctangent processor. Quadrature ratio metric output 540 is depicted with respect to graph 542 having ordinate 544 and abscissa 546, where sine output 536 and cosine output 538 can be graphically shown as sine output plot 548 and cosine output plot 550. Chart 542 also illustrates level 552 , bottom 554 and zero level point 556 . Bottom 554 may be the bottom of a receptacle or the like.

The zero level point 556 may be the lowest level required to obtain a reading. As shown, the quadrature ratio metric output 540 is an angular output independent of the liquid level 552 . Thus, by taking the angular ratio of the two differential outputs (eg, the sine output 536 and the cosine output 538) as the liquid level changes, the quadrature ratio metric output 540 is fluid independent, and the bridge circuit eliminates power from the transducer and Common-mode noise of the circuit, as discussed in more detail in this article. It should be understood that the liquid level 522 is for example purposes only, and could also be illustrated in terms of pressure, force, etc., so that there are two differential outputs. For example, in the case of force, the one level output is the measured force when the force is applied, and the reference output is the normal force when no force is applied.

Figures 5A and 5B provide schematic diagrams of a system 49 with capacitive plates, respectively. The boards are a first variable capacitor 50 and a second variable capacitor 52 implemented within a multilayer printed circuit board (PCB) 54 . The PCB 54 may have a first layer 55a and a second layer 55b, where the first layer may be an I-phase and the second layer may be a Q-phase. The system 49 also includes inverting voltage sources 58, 60 configured to drive the first variable capacitor 50, and the second variable capacitor 52 corresponds to the quadrature signal generated by the pair of inverting voltage sources, wherein the detected The signal represents the differential value of the voltage.

Variable capacitors 50, 52, PCB 54 and/or inverting voltage sources 58, 60 may be integrated into processor 74 configured for quadrature signal generation. It should be understood that the differential capacitance of each signal can be set to about 5pF (picofarads) or more. It should be understood that the differential capacitance of each signal can be set to less than 5pF (picofarads). It is further understood that the depicted layout represents only one possible example of a capacitive plate structure. In one embodiment, the capacitive plate structure may include simple strips provided for each electrode to minimize in-plane capacitance compared to out-of-plane capacitance.

In various embodiments, the variable capacitors 50, 52 may be configured to detect liquid level rise 56a in an area having a pair of sidewalls 62, force changes 56b between sidewalls 62 caused by sidewall movement, Changes in fluids, gases, etc. caused by force and/or some other method, etc. For example, the area can be a reservoir, a pair of plates, etc., whereby the area can be any area in which fluid, pressure, force, etc. can be measured. For example, consider the force exerted on the pedal pad of the brake, accelerator or clutch pedal. That is, fluids, gases, solids, or other force changes between plates acting on the bridge circuit, etc. can be used such that the bridge circuit senses such changes and can be compared to a reference bridge circuit To determine the amount of force, a reference capacitor can be used to determine creep and other principles. It should be understood that arrows 56a, 56b are illustrative only and that the direction of force or level rise may be in any direction between a pair of side walls 62 . Furthermore, it should be understood that at least one of the variable capacitors may be connected in series with another passive element 64 to form a divider with output 66 . Passive components may be capacitors, resistors, inductors, and/or combinations thereof.

6 is a cross-sectional view, generally at 80, of an interdigital electrode capacitance formed by electric field lines arrayed between ground fingers 86 and AC capacitor fingers 88 (see in-field 82 and out-field 84), which helps The purpose is to prevent the oil in which the associated processor is immersed from sticking between the thicknesses of the capacitor plates, thereby increasing the sensing speed and improving the associated response time. The primary viscous force results in the formation of the gap, and where the in-field lines 82 are present at a relatively high density, it should also be understood that when the narrow gap is filled with epoxy such as a coating, this area will not respond to the interaction of the oil, This further helps reduce signal errors.

As further supported by the description above, a feedback loop with an LC circuit is adapted to the received voltages 12, 14 to maintain a constant value to compensate for aging/acidification changes in the dielectric constant associated with the target fluid (eg, oil) , it should also be understood that the difficulty of fluid capacitance measurement is largely due to the change in the dielectric constant of the fluid due to fluid aging/acidification. The feedback loop on the received voltage maintains a constant value based on a predetermined function where the excitation voltages 12, 14 are varied to keep one or more input signals constant.

Additional changes in the corrective feedback loop may include employing a sampling mechanism that exhibits higher resolution than required to allow the input signal to be reduced while still maintaining the output resolution as the excitation voltage reaches its limit. In one non-limiting example, such control may provide a dielectric constant greater than a factor or four times the range (4x) with a given fluid type.

In fluid applications, it is important to balance the RF capacitor sensor relative to the dielectric constant. Balancing the capacitors will define the zero signal point, allowing the level to be measured regardless of the dielectric constant of the fluid. This is important for obvious reasons, such as changes in dielectric constant due to fluid temperature, thickness, breakdown, etc. The balanced capacitor pair requires the same amount of input capacitance (Q _IN ) as the output capacitance (Q _OUT ) accompanying the balanced voltage pair.

An unbalanced circuit as shown in circuit 100 in FIG. 7A illustrates that the voltage V _sen 122 is greater than zero due to the geometry in the control relay and capacitor plates. Circuit 100 in Figure 7A also depicts resistor 103 and a pair of inverting voltage sources (in-phase voltage 102 and out-of-phase voltage 104), thus, inverting voltage sources 102 and 104 produce a balanced voltage pair 106, where V _IN =- _VOUT . Further depicted is a pair of capacitors C _IN 108 and C _OUT 110 connected to inverting voltage sources 102 and 104 , and an additional control capacitor C _crtl1 114 , which is in parallel with capacitor C _IN 108 and is driven by a non-inverting voltage tied at 117 The source 102 is driven and thus has an unbalanced capacitor pair 112 with _Vsen 122 greater than zero.

Referring generally to 120, FIG. 7B is a depiction of a balanced capacitor system 124 with _Vsen 122 equal to zero. Circuit 120 in FIG. 7B also depicts resistor 103 and inverting voltage sources 102 and 104 , which thus produce balanced voltage pair 106 . Further depicted is a balancing system 124 having a pair of capacitors C _IN 108 and C _OUT 110 connected to inverting voltage sources 102 and 104 , and an additional control capacitor C _crtl1 114 , which is _connected to capacitor C _IN 108 are connected in parallel, but driven by the inverting voltage source 104 at junction 118 . This allows unbalanced capacitor pairs to be balanced by the voltage pair. In other words, the control capacitance driven by the opposite branch is equal to the unbalanced portion of the capacitor pair. This can be described by the following equation:

Equation 1: C _IN V _IN + C _ctrl1 V _OUT = C _OUT V _OUT

Equation 2: (C _IN -C _ctrl1 )V _IN =C _OUT V _OUT

A control capacitor can be added to circuit 120 to balance the capacitors using the equation above, where C _IN is greater than C _OUT . The same principle applies by adding a control capacitor and wiring the control capacitor to the opposite branch of the voltage pair, with _Vsen equal to 0.

However, by adding a single control capacitor, parasitic imbalances can occur. To counteract any parasitic losses or stray capacitances, a second control capacitor can be added with any voltage pair. FIG. 7C illustrates circuit 130 with an additional control capacitor C _crtl2 116 added in _parallel with C _IN 108 and similarly connected to non-inverting voltage 102 at junction 132 . Balancing by inserting a control capacitor can be described by the following equation:

Equation 3: C _IN V _IN +C _ctrl1 V _OUT =C _OUT V _OUT +C _ctrl2 V _IN

By definition, with V _OUT = -V _IN , Equation 3 becomes:

Equation 4: (C _IN V _IN -C _ctrl1 )V _IN =(C _OUT V _OUT -C _ctrl2 )V _OUT

It should be understood that C _crtl2 can be added to any unbalanced capacitance, such as the parasitic capacitance of wiring and connectors.

As depicted in Figure 8, a diamond-shaped layout 148 (shown in a pattern of long and short lines) of drivers and driver wires is shown. In addition, FIG. 8 depicts a quadrature signal balanced topology with signal driver 150 and signal driver 152 driving cosine and sine signals through capacitor pairs driven by voltage pairs 102, 104, respectively. . It should be understood that other signal balances and other drivers may be used. Furthermore, in such a final assembly of sensor 146, tuning pads 154, 156 may be necessary in order to balance the final system. The balancing mechanism can be achieved by the same balancing mechanism discussed herein, ie, using sliding tuning capacitors 154 , 156 wired to opposite phases of the voltage pair 102 , 104 . Additionally, the overlap or distance between the tuning pads forms the capacitance required to balance the system, as indicated by distances X _crtl 162 and Y _crtl 164 corresponding to the distances between the tuning pads 154 , 156 and the voltage links 166 , 168 . In particular, non-inverting voltage source 102 is operably connected to voltage junction 168 by conductor 160 and is a distance Y _crtl from tuning pad 156 . Likewise, out-of-phase power supply 104 is operably connected to voltage tie 166 by wire 158 and a distance X _crtl from tuning pad 154 .

Figure 9 depicts that the distance between the two power lines or voltage sources 102, 104 should be closer than the distance between the signal lines 154, 156 under the diamond balanced cancellation of the conductors. It should be understood that the coupling between the signal and any phased power lines is the same, as long as diamonds can be drawn on the connecting wires as shown. When a diamond can be formed, wire cancellation is automatically satisfied if the distance ΔY 172 ≥ ΔX 170; however, the distance ΔY 172 between the signals 156, 154 should be as large as possible within design limits. It should be understood that such a diamond design for any connector wire assembly functions to offset the wires, whether of the IDF or quadrature sensor type. Additionally, a diamond pattern may be combined with the sensor PCB and connecting wire assemblies to eliminate electrical effects.

Referring now back to Figure 8, the parasitic losses of the balanced system may produce undesired capacitances. Accordingly, parasitic losses can be controlled by using tuning pads 154, 156 at each signal driver 150, 152 and diamonds 148 (indicated by dashed lines) for the connector wire assemblies, respectively. Calibrating the system can be used wherever there is a capacitive imbalance. In addition, the sensor plate imbalance can also be tuned in this method. Additionally, connector pins and circuit imbalances can be tuned in the same way.

Figure 10 depicts the layout of the connector pins on the sensor. As shown, a diamond pin pattern 148 is satisfied that connects the wires between the sensor 146 and the circuit 176, thereby ensuring signal decoupling. As shown, the distance between the two power lines 102, 104 is as close as possible 180, 182, while the distance between the two signal lines 154, 156 is as large as 178, 184. Furthermore, although the pin layout is illustrated vertically, it may be any configuration in which the signal lines are separated by at least two power supply lines.

Figure 11 depicts the sensor's tuning pad and drive pin layout. The diamond design 148 is clearly visible in the sensor layout 146 . Again, as shown, the distance between the two power lines 102, 104 is as close as possible, while the distance between the two signal lines 154, 156 is as large as possible. In addition, the signal line crosses the power line perpendicularly.

Figure 12 schematically illustrates an LC inductive sensor with a differential LC oscillator and a Thevenin equivalent circuit. The LC inductive sensor 200 includes a pair of N-channel transistors 204 having a bridge element 208 between the drains 206 . The LC inductive sensor 200 also includes a voltage divider 210 having a pair of passive elements 212 to provide a single differential output 214 . Thus, it should be understood that the LC inductive sensor 200 is a single AC bridge for a single differential output 214 . Additionally, the LC inductive sensor 200 includes a pair of capacitors 216, wherein each capacitor is connected in parallel and to one inductor and one resistor of a pair of inductors 218 and resistors 220, wherein each of the pair Inductor 218 and resistor 220 are in series with each other and with capacitor 216 . Tail current 222 is drawn with a pair of transistors 204 and with a corresponding drain load 206 .

应当理解，电路200和等效电路202的任何阻抗元件可被放大Q倍，并且LC振荡器可以用作具有差分信号的传感器。应当理解，因子Q和I相具有相反方向电流。此外，应该理解，电阻器、电容器或电感器上的任何微小变化都会被放大两倍的尾电流。As shown, the Thevenin equivalent 202 is taken from a pair of inductors 218, so the equivalent source impedance 224a is R _s1 =Q[ω(L+Δ)+R], and the equivalent source impedance 224b is R _s2 =Q [ω(L-Δ)+R]. Additionally, an equivalent differential voltage source V _m 226 and an inverse voltage source V′ _m 228 with source impedance and complementary output strength can be calculated from a single differential output 214 . The Thevenin equivalent 202 transforms the source impedances 224a, 224b by a factor Q. Thus, the circuit acts as an impedance amplifier, multiplying the inductive measure Δ in the inductive sensing circuit. The single differential output 214 for inductive sensing is

It should be understood that any impedance elements of circuit 200 and equivalent circuit 202 can be amplified by a factor of Q, and an LC oscillator can be used as a sensor with a differential signal. It should be understood that the factor Q and I phases have currents in opposite directions. Also, it should be understood that any small change in a resistor, capacitor or inductor will amplify the tail current by a factor of two.

Figure 13 schematically illustrates a current steering bridge circuit 230a having a differential amplifier with a current pool to form a bridge circuit. The tail currents 232 , 234 are absorbed by a pair of transistors 236 , 238 with corresponding drain loads 240 , 242 . The bridge elements between the drains 240 , 242 of the transistors 236 , 238 allow differential current flow between the loads of the drains 240 , 242 . Since the drains 240, 242 are loaded between the transistors 236, 238, the drain loading is balanced and no current flows through the bridge element. However, if there is an impedance that creates an unbalanced condition on the drain load, and if the transistors 236, 238 are turned on, there will be current flowing through the bridge, which can be sensed.

Therefore, by leaving one drain load unchanged, and replacing the other drain load with a sensing element having a residual matching impedance to the drain load, such as but not limited to capacitive, inductive, or configured to sense semiconductor Or an electrical sensing element in which the resistance of metal changes under mechanical strain, and the steering bridge 230 becomes a sensing circuit.

The pilot bridge 230a includes a voltage divider 246 having a pair of bridging impedance elements Z _br 247 with an output V _out 248 between the impedance elements Z _br 247 . Additionally, the pilot bridge 230 includes impedances _Z+Δ 250 and _Z−Δ 252 . Impedances 250 , 252 may be replaced with bridged impedance element 247 to become a bridged impedance element within voltage divider 246 .

FIG. 14A schematically illustrates the pilot bridge circuit 230a of FIG. 13 with a bridge impedance element 247 in place of the impedances 250 , 252 . Voltage inputs 237 , 239 on transistors 236 , 238 are complementary to current sources 232 , 234 and load impedance element Z _br 247 . Thus, the pilot bridge circuit 230b has a similar Thevenin equivalent, as discussed above in FIG. 12 . However, in the current steering bridge circuit 230b, the voltage output 248 is significantly weaker due to the voltage divider 246 (FIG. 13) and the bridge impedance element 247 having a strong impedance (1/gm). Therefore, in sensor applications, the output voltage 248 is differential and proportional to the difference Δ.

确定，其中源V_m264和源V’_m 266是电压源的差分幅度对。Figure 14B schematically illustrates the Thevenin equivalent current steering bridge circuit of Figure 14A. Under Thevenin equivalent circuit 230c, transistor 236 (FIG. 14A), current 232 (FIG. 14A), and impedance 247 (FIG. 14A) of circuit assembly 254a (FIG. 14A) can be combined to have a voltage source V _m 264 and a source impedance Z _s 260 equivalent circuit 258a. Similarly, transistor 238 (FIG. 14A), current 234 (FIG. 14A), and impedance 247 (FIG. 14A) of circuit assembly 254b (FIG. 14A) can be combined into an equivalent with voltage source _V'm 266 and source impedance _Zs 262 circuit 258b. Therefore, the voltage sources 264, 266 are strong enough that the source impedances 260, 262 become smaller than the bridge impedances 250, 252 so that the output voltage 248 can pass through the equation

Determine where source _Vm 264 and source _V'm 266 are differential magnitude pairs of voltage sources.

Figure 15A schematically illustrates the differential impedance current steering bridge circuit of Figure 14A. The current steering bridge circuit 230d with quarter bridge includes a differential voltage source 270 including a voltage source V _m 264 and a voltage source V' _m 266 . The differential AC voltage source 270 has a 4Mhz frequency and an amplitude _Vm . It should be understood that the frequency of the differential voltage source may be greater or less than 4Mhz. The sign convention on the voltage sources 264, 266 indicates the phase of the AC voltage. Source impedances Z _s 260 , 262 are connected to voltage source V _m 264 and voltage source V′ _m 266 . The differential voltage source 270 drives a bridge that includes the impedance pair at Z _ref +Δ 272 and Z _ref 274 . Impedance pair 272, 274 is a pair of capacitors, but is not limited to capacitors, and as discussed below, may be inductors, resistors, and/or other elements. Voltage divider 276 is connected to the bridge at node 'a' 286 and includes impedance pair Z ₁ 278 and Z ₂ 280 . It should be understood that the impedance pair 278, 280 may be a pair of capacitors, inductors, resistors, any combination thereof, and/or other elements.

另外，节点‘a’286处的电桥的输出电压282的频率过高，并且通常是必须要衰减且需要调整相位的延迟信号(相位滞后)。作为结果，电流导引桥230c的分压器276充当无源网络来衰减和调整相位。应当理解，电流导引桥电路230d可适用于对差分信号进行解码的各种感测元件，包括电容式、电感式或电阻式感测元件。节点‘b’288处的分压器276的输出284被导向被配置用于LC振荡器的信号处理器290中。因此，电流导引桥电路230d是提供差分信号输出284的单AC电桥。The differential impedance detects the difference Δ=(Z _ref+Δ −Z _ref ) of the impedance pair. When Δ and source impedance _Zs 260, 262 are small, the output 282 at bridge node 'a' 286 becomes

Additionally, the frequency of the output voltage 282 of the bridge at node 'a' 286 is too high and is typically a delayed signal (phase lag) that must be attenuated and phase adjusted. As a result, the voltage divider 276 of the current steering bridge 230c acts as a passive network to attenuate and adjust the phase. It should be understood that the current steering bridge circuit 230d can be adapted to various sensing elements for decoding differential signals, including capacitive, inductive or resistive sensing elements. The output 284 of the voltage divider 276 at node 'b' 288 is directed into a signal processor 290 configured for use in an LC oscillator. Thus, current steering bridge circuit 230d is a single AC bridge providing differential signal output 284 .

Figure 15B schematically illustrates the differential impedance current steering bridge circuit of Figure 14A. The current steering bridge circuit _230e includes a differential AC voltage source 270 having a frequency of 4Mhz and an amplitude Vm. It should be understood that the frequency of the differential voltage source may be greater or less than 4Mhz. The differential voltage source 270 includes a voltage source V _m 264 and a voltage source V' _m 266 . The sign convention on the voltage sources 264, 266 indicates the phase of the AC voltage.

分压器276在节点‘a’286处连接到电桥，并且包括阻抗对Z₁ 278和Z₂ 280。应当理解，阻抗对278、280可以是一对电容器、电感器、电阻器、其任何组合和/或其他元件。分压器276提供信号处理器290(图15A)所需的适当衰减和相位。因此，电流导引桥电路230e是提供差分信号输出284的单AC电桥。The differential voltage source 270 drives a bridge that includes the sense coil pair Lref + _Δ292 and _Lref 294. The coil pair 272, 274 is a pair of inductors, but is not limited to inductors, and as discussed previously, may be capacitors, resistors, and/or other elements. The coupler 296 is positioned relative to the pair of sense coils 272, 274 so that the coupler 296 can move along the pair of sense coils 272, 274 such that the position of the coupler is steered by the current at bridge node 'a' 286 Output 282 generates a differential signal detected where

Voltage divider 276 is connected to the bridge at node 'a' 286 and includes impedance pair Z ₁ 278 and Z ₂ 280 . It should be understood that the impedance pair 278, 280 may be a pair of capacitors, inductors, resistors, any combination thereof, and/or other elements. The voltage divider 276 provides the appropriate attenuation and phase required by the signal processor 290 (FIG. 15A). Thus, current steering bridge circuit 230e is a single AC bridge providing differential signal output 284 .

16 schematically illustrates the differential capacitive current steering bridge circuit 230f of FIGS. 14A-14B, 15A-15B. The current steering bridge circuit 230f is illustrated as having a differential AC voltage source 270 having a voltage source V _m 264 and a voltage source V′ _m 266 . The sign convention on the voltage sources 264, 266 indicates the phase of the AC voltage. The differential voltage source 270 drives the bridge, which is illustrated as having the capacitance pair C _ref +Δ300 and C _ref 302 . It should be understood that while the differential capacitive current steering bridge circuit 230f is illustrated with capacitive pairs, this is non-limiting and may be replaced with impedance pairs, resistor pairs, and/or combinations of capacitors, inductors, and resistors. The voltage divider 276 is connected to the bridge at node 'a' 286 and includes an impedance pair illustrated as a capacitor Z ₁ 278 and a second impedance Z ₂ 280 . It should be understood that the impedance pair 278, 280 may be a pair of capacitors, inductors, resistors, any combination thereof, and/or other elements.

Capacitor C _ref +Δ300 can be printed on PCB 54 ( FIG. 5B ) and can be in contact with a measurable medium 304 such as gas, pressure, fluid that can change or vary based on force, liquid level, etc. Wait. In some embodiments, a force may be exerted on a fluid, gas, pressure, etc. that can be measured by capacitor C _ref +Δ300. In other embodiments, as discussed in more detail herein, the force may be applied directly to a pair of plates, sidewalls, etc., which may be detected by capacitor Cref+ _Δ300 or the space therebetween The force can be sensed by capacitor C _ref +Δ300 to determine the force. Furthermore, it should be understood that the force applied to the fluid, gas, pressure build up, change space, etc. may be at various angles (0 degrees to 360 degrees) relative to C _ref + Δ 300 and illustrated by directional arrow 306 . . As the measurable medium 304 changes in any direction, as indicated by directional arrow 306 , the measurable medium 304 changes such that the change in the measurable medium 304 is detected by at least capacitor C _ref +Δ 300 and output by the differential signal output 282 , due to the change in capacitance Δ as the measurable medium 304 in contact with the capacitor 300 changes. The voltage divider 276 provides the appropriate attenuation and phase required by the signal processor 290 (FIG. 15A). Thus, the current steering bridge circuit 230f is a single AC bridge that provides the differential signal output 284 .

It should be understood that the capacitor C _ref +Δ 300 could be replaced by a discrete component, and that the pilot bridge circuit 230f could behave in the same manner using the amount or level of the measurable medium 304 moving along the sensing electrode pair, due to the The variation Δ varies with the amount or level of the measurable medium 304 .

It will be appreciated that since the differential AC voltage source 270 (FIGS. 14A-16) operates at 4 MHz, the advantage over conventional capacitive sensor designs is that this embodiment operates at nearly 400 times higher frequency than conventional capacitive sensors . Therefore, the source impedance becomes 400 times lower than the conventional capacitive sensor, making the capacitive sensor of this embodiment have much better noise performance.

It should be understood that the above-described embodiments are not limited to differential voltage sources as described above. In a non-limiting example, an LC oscillator circuit with a center tap can be transformed into a differential voltage source with transformed series resistance R and phasor _Vm . The equivalent source impedance _Rs becomes the Q times R of the original circuit, and _Vm can be estimated from Q and the tank impedance.

Also, if the inductor does not have a center tap for powering, but instead has a pair of identical resistors to power the circuit, the circuit will function almost the same as a circuit with a center-tapped inductor, however since the supply resistor pairs of Q quality factor loss, there will be a lower voltage swing. Such a differential voltage source structure is advantageous because it provides calibration for proper balance of differential voltage pairs _Vm and _V'm using trimming of supply resistor pairs, which is inherently easier than using inductors . Furthermore, the reason such a voltage source configuration is advantageous is that in certain applications, the average voltage of V _out can be lowered to eliminate bias voltages downstream of the circuit, such that when the sensing element is a conducting element.

Figure 17A schematically illustrates a center-tapped, dual-bridge differential inductive current steering bridge circuit with two variable inductors. The current steering bridge circuit 310 includes a pair of resistors 312 , 314 , a capacitor 324 , a tail current 330 and two bridges 315 , 319 . Although illustrated as a pair of resistors 312, 314 and capacitor 324, this is non-limiting and a pair of resistors 312, 314 may be a pair of inductors, a pair of capacitors, and/or a combination thereof. Capacitor 324 may be a resistor and/or an inductor. A first bridge 315 with node 317 separates a first pair of sensing elements comprising a first sensing element 316 and a second sensing element 318, wherein the first sensing element 316 has incremental changes. That is, the first sensing element 316 is configured to detect changes in quantities in the measurable medium 304, such as fluids, pressures, gases that may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. changes in wait. As discussed in greater detail herein, the second sensing element 318 is configured to detect a reference value 306a that references the measurable medium 304a (FIG. 16). The first and second sensing elements 316, 318 may be a pair of inductors, a pair of capacitors, a pair of resistors, and/or combinations thereof. It should be understood that the first sensing element 316 configured to detect a change in the amount in the measurable medium 304 ( FIG. 16 ) is non-limiting and that the second sensing element 318 may be configured to detect the measurable medium 304 (FIG. 16), while the first sensing element 316 may be configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16). The first bridge 315 outputs the first differential signal 326 from the node 317 . The first differential signal 326 may contain information related to the difference between the measurable medium 304 ( FIG. 16 ) sensed by the first sensing element 316 and the reference measurable medium 304a sensed by the second sensing element 318 .

The second bridge 319 has a second node 321 that separates a second pair of sense elements including a third sense element 320 and a fourth sense element 322, wherein the fourth sense element 322 has Incremental changes. That is, the fourth sensing element 322 is configured to detect changes in the amount of the measurable medium 304 (FIG. 16), such as fluids that may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. , pressure, gas, etc., as discussed in more detail herein. The third sensing element 320 is configured to detect the reference value 306a of the measurable medium 304a (FIG. 16), as discussed in greater detail herein. The third and fourth sensing elements 320, 322 may be a pair of inductors, a pair of capacitors, a pair of resistors, and/or combinations thereof. It should be understood that the fourth sensing element 322 configured to detect a change or other change in the amount of the force direction 306 in the measurable medium 304 (FIG. 16) is non-limiting and that the third sensing element 320 may be configured For detecting changes or other changes in the amount of force in the measurable medium 304 (FIG. 16), the fourth sensing element 322 may be configured to detect the reference value 306a (FIG. 16) of the measurable medium 304 (FIG. 16). ). The second bridge 319 outputs the second differential signal 328 from the second node 321 . The second differential signal 328 may include sensing with the measurable medium 304 (FIG. 16) sensed by the fourth sensing element 322 and the reference measurable medium 304a (FIG. 16) sensed by the third sensing element 320 to the difference-related information.

Additionally, in some embodiments, the first differential signal 326 and the second differential signal 328 are input into a divider 329 to divide or convert the signals into a ratio indicated by the ratio metric output 329a. It should be understood that the bridge circuit 310 may be a center-tapped LC circuit and include more than one set of sense coils. Since the inductance of the resonator has a dual function, it is possible to separate the sense coils. First, as a resonator coil, and second, as a sense coil when modulated using an anti-eddy current plate. That is, a first differential output 326 may be output from a first electrical bridge 315 between a pair of sensing elements 316, 318, and a second electrical output 326 may be output from two separate and distinct sensing elements 320, 322 Bridge 319 generates second differential signal 328 . Thus, it is possible to be in one location such as a receptacle, tank, between a compressible pair of side walls or panels, etc., or between more than one or separate receptacles, tanks, compressible second pair of side walls or panels, etc. etc. use an LC oscillator circuit 310.

Figure 17B schematically illustrates a center-tapped, differential bridge circuit 332 with four variable inductors. The bridge circuit 332 includes a pair of resistors 334 , 336 , a capacitor 350 , a tail current 352 , and two bridges 335 , 339 . Although illustrated as a pair of resistors 312, 314 and capacitor 350, this is non-limiting and a pair of resistors 312, 314 may be a pair of inductors, a pair of capacitors, and/or a combination thereof. Capacitor 350 may be a resistor and/or an inductor. The first bridge 335 has a node 337 that separates a first pair of sense elements including a first sense element 338 and a second sense element 340, wherein the first sense element 338 and the second sense element The elements 340 are all variable, and the first sensing element 338 has incremental changes. The first and second sensing elements 338, 340 may be a pair of inductors, a pair of capacitors, a pair of resistors, and/or combinations thereof.

That is, the first sensing element 338 is configured to detect changes in the amount of the measurable medium 304 (FIG. 16), such as fluids that may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. , pressure, force, gas, etc. The second sensing element 340 is configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16), as discussed in greater detail herein. It should be understood that the first sensing element 338 configured to detect a change in the amount in the measurable medium 304 ( FIG. 16 ) is non-limiting and that the second sensing element 340 may be configured to detect the measurable medium 304 (FIG. 16), while the first sensing element 338 may be configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16). The first bridge 335 outputs the first differential signal 346 from the first node 337 . The first differential signal 346 may include sensing with the measurable medium 304 (FIG. 16) sensed by the first sensing element 338 and the reference measurable medium 304a (FIG. 16) sensed by the second sensing element 340 to the difference-related information.

The second bridge 339 has a second node 343 that separates a second pair of sense elements including a third sense element 342 and a fourth sense element 344, wherein the third sense element 342 and The fourth sensing elements 344 are all variable, and the fourth sensing elements 344 have incremental changes. The third and fourth sensing elements 342, 344 may be a pair of inductors, a pair of capacitors, a pair of resistors, and/or combinations thereof. That is, the fourth sensing element 344 is configured to detect changes in quantities in the measurable medium 304 (FIG. 16), such as fluids that may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. , pressure, force, gas, etc., as discussed in more detail herein. The third sensing element 342 is configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16), as discussed in greater detail herein. It should be understood that the fourth sensing element 344 configured to detect a change in the amount in the measurable medium 304 ( FIG. 16 ) is non-limiting and that the third sensing element 342 may be configured to detect the measurable medium 304 (FIG. 16), while the fourth sensing element 344 may be configured to detect the reference value 306a (FIG. 16) of the measurable medium 304 (FIG. 16). The second bridge 339 outputs the second differential signal 348 from the second node 343 . The second differential signal 348 may include sensing with the measurable medium 304 (FIG. 16) sensed by the fourth sensing element 344 and the reference measurable medium 304a (FIG. 16) sensed by the third sensing element 342 to the difference-related information.

Furthermore, in some embodiments, the first differential signal 346 and the second differential signal 348 are input into a divider 349 to divide or convert the signals into a ratio indicated by the ratio metric output 349a. It should be understood that the bridge circuit 332 may have dual LC oscillators configured to operate from more than one or separate reservoirs, tanks, second pair of sidewalls or plates, etc. that are compressible and independent of each other Generates two outputs.

As mentioned above, although a center-tapped LC circuit differential voltage source structure can be used for quarter bridges, such structures can also be used for half-bridge and full-bridge structures.

FIG. 17C schematically illustrates the single-bridge differential circuit 402 . Bridge circuit 402 includes a pair of inductors 404 , 406 , tail current 408 and bridge 410 . Although illustrated as a pair of inductors 404, 406, this is non-limiting, and the pair of inductors may be a pair of resistors, a pair of capacitors, and/or combinations thereof. The bridge 410 has a node 412 that separates a first pair of sense elements including a first sense element 414 and a second sense element 416, wherein the first sense element 414 has an incremental change. The first and second sensing elements 414, 416 may be a pair of inductors, a pair of capacitors, a pair of resistors, and/or combinations thereof. That is, the first sensing element 414 is configured to detect changes in the amount of the measurable medium 304 (FIG. 16), such as fluids that may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. , pressure, gas, etc. The second sensing element 416 is configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16), as discussed in greater detail herein. It should be understood that the first sensing element 414 configured to detect a change in the amount in the measurable medium 304 ( FIG. 16 ) is non-limiting and that the second sensing element 416 may be configured to detect the measurable medium 304 (FIG. 16), while the first sensing element 414 may be configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16). Bridge 410 outputs differential signal 418 from node 412 . The differential signal 418 may contain the sensed signal between the measurable medium 304 (FIG. 16) sensed by the first sensing element 414 and the reference measurable medium 304a (FIG. 16) sensed by the second sensing element 416. Difference-related information.

FIG. 17D schematically illustrates a differential bridge circuit 420 with dual bridges 422 , 424 . The bridge circuit 420 also includes a pair of inductors 426 , 427 and a tail current 431 . Although illustrated as a pair of inductors 426, 427, this is non-limiting, and the pair of inductors 426, 427 may be a pair of resistors, a pair of capacitors, and/or a combination thereof. The first bridge 422 has a first node 428 that separates a first pair of sense elements including a first sense element 429 and a second sense element 430, wherein the first sense element 429 is Variable, and the first sensing element 429 has incremental changes.

That is, the first sensing element 429 is configured to detect changes in quantities in the measurable medium 304, such as fluid, pressure, force, etc., which may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. , gas, etc. The second sensing element 430 is configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16), as discussed in greater detail herein. It should be understood that the first sensing element 429 configured to detect a change in the amount in the measurable medium 304 ( FIG. 16 ) is non-limiting and that the second sensing element 430 may be configured to detect the measurable medium 304 (FIG. 16), while the first sensing element 429 may be configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16). The first bridge 422 outputs the first differential signal 432 from the first node 428 . The first differential signal 432 may contain a correlation to the difference sensed between the measurable medium 304 sensed by the first sensing element 429 and the reference measurable medium 304a (FIG. 16) sensed by the second sensing element 430 Information.

The second bridge 424 has a second node 434 that separates a second pair of sense elements including a third sense element 436 and a fourth sense element 438, wherein the third sense element 436 is Variable, and the third sensing element 436 has incremental changes. That is, the third sensing element 436 is configured to detect changes in quantities in the measurable medium 304, such as fluids, pressures, gases that may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. Variations among others, as discussed in more detail herein. The fourth sensing element 438 is configured to detect the reference value 306a of the measurable medium 304a, as discussed in greater detail herein. It should be understood that the third sensing element 436 configured to detect a change in the amount in the measurable medium 304 ( FIG. 16 ) is non-limiting and that the fourth sensing element 438 may be configured to detect the measurable medium 304 While the third sensing element 436 may be configured to detect the reference value 306 a of the measurable medium 304 . The second bridge 424 outputs the second differential signal 440 from the second node 434 . The second differential signal 440 may include sensing with the measurable medium 304 (FIG. 16) sensed by the third sensing element 436 and the reference measurable medium 304a (FIG. 16) sensed by the fourth sensing element 438 to the difference-related information.

Additionally, in some embodiments, the first differential signal 432 and the second differential signal 440 are input into a divider 442 to divide or convert the signals into a ratio indicated by the ratio metric output 444 .

FIG. 17E schematically illustrates a single bridge ratio metric circuit 450 . The bridge circuit 450 includes a pair of sensing elements including a first sensing element 452 and a second sensing element 454, wherein the first sensing element 452 has incremental changes. Although the first and second sensing elements 452, 454 are illustrated as a pair of inductors, this is non-limiting and may be a pair of resistors, a pair of capacitors, and/or combinations thereof. That is, the first sensing element 452 is configured to detect changes in quantities in the measurable medium 304, such as fluid, pressure, force, etc., which may be caused by changes in liquid level, forces in the force direction 306 (FIG. 16), etc. , gas, etc. The second sensing element 454 is configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16), as discussed in greater detail herein. It should be understood that the first sensing element 452 configured to detect a change in the amount in the measurable medium 304 ( FIG. 16 ) is non-limiting and the second sensing element 454 may be configured to detect the measurable medium 304 (FIG. 16), while the first sensing element 452 may be configured to detect the reference value 306a (FIG. 16) of the measurable medium 304a (FIG. 16).

Bridge circuit 450 also includes tail current 456 and bridge 458 . The bridge 458 has a node 460 that separates the first element 462 from the second element 464 . The first and second elements 462, 464 may be a pair of inductors, a pair of resistors, a pair of capacitors, and/or combinations thereof. Bridge 458 outputs ratio metric signal 466 from node 460 . The ratiometric signal 466 may include a sensed between the measurable medium 304 (FIG. 16) sensed by the first sensing element 452 and the reference measurable medium 304a (FIG. 16) sensed by the second sensing element 454 information about ratios or division differences.

Referring back to Figures 17C-17D and Figures 4-5, it should be understood that the differential bridge circuit 420 may have dual AC bridges for ratiometric output. The two differential outputs are independent of, or cancel out, common-mode noise commonly found in transducers and circuits through AC bridges. Additionally, the ratio metric output 444 is the ratio of each of the differential output signals 432 , 440 . Additionally, ratiometric measurements can be applied to inductive, capacitive, or resistive measurements. It should be understood that the circuits described herein can simultaneously remove common mode noise when designing two differential signals.

Reference is now made to FIG. 18 which schematically illustrates the ratiometric output of a differential capacitive current steering bridge circuit 354 including circuit 230g and differential capacitive current steering bridge circuit 230f (FIG. 16). The current steering bridge circuit 230g includes a differential AC voltage source having a voltage source V _m 358 and a voltage source V′ _m 360 . The sign convention on the voltage sources 358, 360 indicates the phase of the AC voltage. A differential voltage source drives a bridge that includes a capacitor pair C _oil 362 and C _ref1 364 . It should be understood that while the differential capacitive current steering bridge circuit 230g is illustrated as having capacitive pairs, similar to the circuit 230f discussed above with respect to FIG. 16, this is non-limiting, and impedance pairs, resistor pairs, and/or A combination of capacitors, inductors and resistors are used instead.

The voltage divider is connected to the bridge circuit at node 366 and includes an impedance pair illustrated as capacitor C ₁ 370 and a second impedance Z ₂ 372 . It should be understood that the impedance pair 370, 372 may be a pair of capacitors, inductors, resistors, any combination thereof, and/or other elements. Capacitor C _oil 362 may be printed on a PCB board and configured to detect changes in quantity in measurable medium 304 (FIG. 16), such as may be caused by changes in liquid level, force in force direction 306 (FIG. 16), etc. changes in fluids, pressures, gases, etc. In some embodiments, the capacitor C _oil 362 and PCB can be submerged in fluid, surrounded by gas, positioned where there is pressure, positioned between compressed media, etc., so that changes in force can be detected. An output that may indicate changes in force, fluid, gas, pressure, etc. is the first differential output 378 taken from the voltage divider node 374 . The same can happen in the reference capacitor 364 so that the outputs can be compared or used to define ratios. It should be understood that references may be used to determine dielectric fluids, material creep, and the like.

In this embodiment, ratiometric output 380 may be generated by divider 380a by taking the ratio of output V _x 356 of differential capacitive current steering bridge circuit 230f divided by output 378 of differential capacitive current steering bridge circuit 230g. The output _Vx 356 measures the measurable medium 304, while the output _Vref 378 generates a reference capacitance value from the reference measurable medium 304a. The electrodes of the capacitor C _oil 362 may be subjected to forces, pressures, fluids, etc. according to the application understood by those skilled in the art. By determining the ratio between output 356 and output 378, force type (ie, caused by gas, fluid, or some other medium), fluid type, temperature, common noise, and electromagnetic interference can now be ignored.

Thus, according to the present embodiment described above, noise reduction in inductive sensing is accomplished either by RF frequency manipulation of the sensor plate or by a ratiometric processing of the two output signals.

In accordance with the above disclosure, the capacitive sensing mechanism of the present invention utilizes ratiometric and differential concepts in order to eliminate most variations associated with undesired effects, the differential structure of the sensing element further eliminates most common mode effects. Other considerations include presenting the ratio of the two signals generated in order to further reduce common mode effects. The use of an LC-type drive mechanism further allows for noise immunity and low emissions from drive harmonics.

It should be understood that inductive sensors with LC oscillators can be used as part of a current steering bridge pair of capacitive sensors, which are suitable for Detect liquid level, fluid quality, acceleration, humidity, pressure or some gas concentrations. Furthermore, LC inductive circuits have good differential voltage sources to drive the bridges shown or modified bridges to measure quantities in a ratiometric manner to compensate for temperature, electromagnetic interface or mechanical variations of the sensor device.

Furthermore, it should be understood that discrete components may be substituted for any of the sensing elements described above, including but not limited to capacitors, inductors, or resistors.

Although particular embodiments have been shown and described herein, it should be understood that various other changes and modifications can be made without departing from the spirit and scope of the claimed subject matter. Furthermore, although various aspects of the claimed subject matter have been described herein, these aspects need not be used in combination. Accordingly, the appended claims are intended to cover all such changes and modifications as come within the scope of the claimed subject matter.

Claims (20)

1. A system comprising: processor; a first bridge circuit communicatively coupled to the processor, the first bridge circuit having: a first pair of differential voltage sources configured to drive the first bridge circuit; and a first pair of capacitors that generate a first pair of measurement signals, one capacitor of the first pair of capacitors positioned in contact with the first measurable medium, the first pair of measurement signals being independent of each other and based on the output of the respective capacitor; A second bridge circuit communicatively coupled to the processor, the second bridge circuit having: a second pair of differential voltage sources configured to drive the second bridge circuit; and a second pair of capacitors generating a second pair of measurement signals, one capacitor of the second pair of capacitors being positioned in contact with the second measurable medium, the second pair of measurement signals being independent of each other and based on the output of the respective capacitor, wherein the first bridge circuit outputs a first output signal to a divider, and the second bridge circuit outputs a second output signal to the divider, and wherein a ratiometric output signal is generated by the divider, the ratiometric output signal being determined by the processor as a ratio of the first output signal to the second output signal. 2. The system of claim 1, further comprising: a first pair of sensing elements communicatively coupled to the first pair of capacitors, the first pair of sensing elements defining a first voltage divider, the first pair of measurement signals passing through the first pair of sensing elements an input, and the first voltage divider is configured to output the first output signal to the divider, the first pair of sensing elements from a set of capacitors, inductors and resistors and combinations thereof; as well as A second pair of sensing elements communicatively coupled to the second pair of capacitors, the second pair of sensing elements defining a second voltage divider, the second pair of measurement signals passing through the second pair of sensing elements input, and the second voltage divider is configured to output the second output signal to the divider, the second pair of sensing elements from a set of capacitors, inductors and resistors, and combinations thereof. 3. The system of claim 1, wherein the first measurable medium is different from the second measurable medium. 4. The system of claim 3, wherein one capacitor of the first pair of capacitors positioned in contact with the first measurable medium is configured to detect a capacitor in the first measurable medium Variety. 5. The system of claim 4, wherein the first pair of measurement signals are differential capacitance measurements corresponding to contacting the first pair of capacitors positioned in contact with the first measurable medium. the force of a capacitor. 6. The system of claim 4, wherein the first pair of measurement signals are differential capacitance measurements corresponding to contacting the first pair of capacitors positioned in contact with the first measurable medium pressure of a capacitor. 7. The system of claim 4, wherein the first pair of measurement signals are differential capacitance measurements corresponding to contacting the first pair of capacitors positioned in contact with the first measurable medium A capacitor fluid. 8. A system comprising: processor; a first bridge circuit communicatively coupled to the processor, the first bridge circuit having: a first pair of differential voltage sources configured to drive the first bridge circuit; and a first pair of inductors that generate a first pair of measurement signals, one inductor of the first pair of inductors positioned in contact with the first measurable medium, the first pair of measurement signals being independent of each other and based on respective inductances output of the device; A second bridge circuit communicatively coupled to the processor, the second bridge circuit having: a second pair of differential voltage sources configured to drive the second bridge circuit; and A second pair of inductors that generate a second pair of measurement signals, one of which is positioned in contact with the second measurable medium, the second pair of measurement signals being independent of each other and based on respective inductances the output of the device, wherein the first bridge circuit outputs a first output signal to a divider, and the second bridge circuit outputs a second output signal to the divider, and wherein a ratiometric output signal is generated by a divider, the ratiometric output signal being determined by the processor as a ratio of the first output signal to the second output signal. 9. The system of claim 8, further comprising: a first pair of sensing elements communicatively coupled to the first pair of inductors, the first pair of sensing elements defining a first voltage divider through which the first pair of measurement signals are sensed element input, and the first voltage divider is configured to output the first output signal to the divider, the first pair of sensing elements from a set of capacitors, inductors and resistors and combinations thereof ;as well as A second pair of sensing elements communicatively coupled to the second pair of inductors, the second pair of sensing elements defining a second voltage divider through which the second pair of measurement signals are sensed element input, and the second voltage divider is configured to output the second output signal to the divider, the second pair of sensing elements from a set of capacitors, inductors and resistors and combinations thereof . 10. The system of claim 8, wherein the first measurable medium is different from the second measurable medium. 11. The system of claim 10, wherein one inductor of the first pair of inductors positioned in contact with the first measurable medium is configured to detect the first measurable medium changes in. 12. The system of claim 11, wherein the first pair of measurement signals are differential inductance measurements corresponding to contacts in the first pair of inductors positioned in contact with the first measurable medium the force of an inductor. 13. The system of claim 11, wherein the first pair of measurement signals are differential inductance measurements corresponding to contacts in the first pair of inductors positioned in contact with the first measurable medium the pressure of an inductor. 14. The system of claim 11, wherein the first pair of measurement signals are differential inductance measurements corresponding to contacts in the first pair of inductors positioned in contact with the first measurable medium of an inductor fluid. 15. A system comprising: processor; a first bridge circuit communicatively coupled to the processor, the first bridge circuit having: a first pair of differential voltage sources configured to drive the first bridge circuit; and a first pair of resistors that generate a first pair of measurement signals, one resistor of the first pair of resistors positioned in contact with the first measurable medium, the first pair of measurement signals being independent of each other and based on respective resistances output of the device; A second bridge circuit communicatively coupled to the processor, the second bridge circuit having: a second pair of differential voltage sources configured to drive the second bridge circuit; and A second pair of resistors that generate a second pair of measurement signals, one resistor of the second pair of resistors being positioned in contact with the second measurable medium, the second pair of measurement signals being independent of each other and based on respective resistances the output of the device, and wherein the first bridge circuit outputs a first output signal to a divider, and the second bridge circuit outputs a second output signal to the divider, and wherein a ratiometric output signal is generated by a divider, the ratiometric output signal being determined by the processor as a ratio of the first output signal to the second output signal. 16. The system of claim 15, further comprising: a first pair of sensing elements communicatively coupled to the first pair of resistors, the first pair of sensing elements defining a first voltage divider through which the first pair of measurement signals are sensed element input, and the first voltage divider is configured to output the first output signal to the divider, the first pair of sensing elements from a set of capacitors, inductors and resistors and combinations thereof ;as well as A second pair of sensing elements communicatively coupled to the second pair of resistors, the second pair of sensing elements defining a second voltage divider through which the second pair of measurement signals are sensed element input, and the second voltage divider is configured to output the second output signal to a divider, the second pair of sensing elements from a set of capacitors, inductors and resistors and combinations thereof. 17. The system of claim 15, wherein: the first measurable medium is different from the second measurable medium, and One resistor of the first pair of resistors positioned in contact with the first measurable medium is configured to detect a change in the first measurable medium. 18. The system of claim 17, wherein the first pair of measurement signals are differential resistance measurements corresponding to contacts in the first pair of resistors positioned in contact with the first measurable medium of the force of a resistor. 19. The system of claim 17, wherein the first pair of measurement signals are differential resistance measurements corresponding to contacts in the first pair of resistors positioned in contact with the first measurable medium the voltage of a resistor. 20. The system of claim 17, wherein the first pair of measurement signals are differential resistance measurements corresponding to contacts in the first pair of resistors positioned in contact with the first measurable medium of a resistor of fluid.

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