SU782150A1 - Device for converting bridge sensor signal into frequency - Google Patents

Description

one

The invention relates to a measurement technique and can be used in devices for measuring non-electric quantities.

A voltage-to-frequency converter is known, comprising an integrator, a comparator, a key, a trigger, a coincidence element, in which the output frequency signal is generated as a result of accumulation of the measured voltage on the integrator using a reference voltage over a stable time interval.

The closest in technical essence to the present invention is a device for converting electric signals of bridge sensors into a frequency comprising a bridge sensor, a scale amplifier, an integrator, a summing amplifier, a comparator, a power source, a reference voltage source, a code-analog converter, a frequency divider circuit match, pulse generator and counter. In this device, a code-to-analog converter provides n comparison levels on one of the inputs of a summing amplifier, to the other two inputs of which signals are supplied from the integrator output and from the source output.

support stress. At the moment of equality of these signals, the summing amplifier through the comparator and the coincidence circuit allows the passage of the pulse from the generator to the divider, the factors and the counter. The frequency divider switches the power source of the sensor with a frequency n times lower than the output frequency. Thus, in the known device 10, the sensor is powered by a rectangular voltage, whose frequency varies {2J.

t

A disadvantage of the known device is a change in a large frequency range of the sensor power, which increases the effect of the distributed parasitic capacitances of the sensor itself and the communication line between the sensor and the converter, which cause a transient process voltage supply. The effects of the power supply fronts are most pronounced with increasing output frequency. 25 The purpose of the invention is to improve the accuracy of conversion in a wide dynamic range of input signals. The goal is achieved by the fact that the voltage converter is 30 frequency, containing a bridge circuit.

A frequency generator, the output of which is connected to the first input of the matching element and a counting input of the trigger, the output of which is connected to the second input of the coincidence element and controls the input of the key, which is connected through the first resistor to one of the vertices of the diagonal of the bridge circuit and the output through the integrator is connected to the input of the main comparator, as well as an amplifier, the output of which is connected through the second resistor to the input of the integrator, and the inputs of the amplifier are connected to the measuring diagonal of the circuit, and the source power, the output of which through the switch is connected to the bridge circuit, is introduced (n + 1) formers, n comparators, a controlled frequency divider and a voltage divider with n outputs, the inputs of which are connected to the diagonal | The power supply of the bridge circuit and n outputs are connected to the first inputs. Additional n comparators, the second inputs of which are interconnected and with the amplifier output, and outputs n of the comparators are connected by the first inputs of n formers, the other inputs of which are interconnected with the first input of the (n + 1) -th format and the top of the diagonal of the bridge circuit The outputs of the driver are connected to the control inputs of the controlled frequency divider, the counting input of which is connected to the trigger output, and the output is connected to the control input of the switch, while the second input (part 4-1) of the driver union of a main outlet of the comparator, and the output from the set input of the flip-flop.

In this case, each driver is formed by two inverters and three elements of coincidence, the first element of which is connected to the first input of the former through the first inverter and to the first input of the second coincidence element, the second input of which is connected via the second inverter to the second input of the former This match and the outputs of the two first match elements are connected to the inputs of the third match element, the output of which is the output of the driver.

FIG. 1 shows a structural electrical circuit of the device; in fig. 2 shows time diagrams of the voltage variation at the outputs of the switch (a), the amplifier (b), the integrator (c) of the comparator (d) and the driver (e).

The device for converting the signal of a bridge sensor to a frequency contains a power source 1 (Fig. 1), a switch 2, a bridge circuit 3, an amplifier 4, resistors 5 and b, a key 7, an integrator 8, a main comparator 9, a trigger 10, a generator 11, element 12 coincidence, voltage divider 13 with n outputs, n additional comparators 14.-16, (n + 1) additional formers 17–20, right divider 21 frequencies. -.

Each driver contains (in Figure 1 a driver 17 is disclosed) two inverters 22 and 24 and three elements 23, 25 and 26 of coincidence.

0 The device operates as follows.

During the interval t, the position of switch 2 is such that the voltage at point B relative to point A is positive (Fig. 2a). The voltage from the output of the sensor goes to the input of amplifier 4 and through resistor 5 goes to the input of integrator 8. At the beginning of the interval t the position of the trigger 10 is such that the key 7 is open. Since the voltage at point B is much greater than the output voltage of amplifier 4, a negative voltage accumulates at the output of integrator 8 (Fig. 2c). Then, when the pulse arrives from the frequency generator 11, the trigger is thrown, the key 7 is turned off, only the voltage from the output of the amplifier 4 is applied to the input of the integrator 8, therefore the accumulator element of the integrator begins to recharge, changing the negative output voltage of the integrator to the positive side and to a certain

from the moment it passes the zero level, the comparator 9 will change its state to the opposite (FIG. 2d) and through the driver 17 will give permission to the input of the trigger 10, but the trigger will trigger from the first trigger following this pulse coming to the counting input of the trigger 11 From the output of the trigger, time is controlled, the flow of which to the integrator 8 receives the reference voltage. This control is carried out by means of supplying a pulse of control from trigger 10 to key 7. Thus, the integrator 8 continuously supplies voltage from the output of the amplifier

g 4, But when the integrator passes the output voltage through the zero level, it is triggered by the reference voltage of the point B 3 of the time between two pulses from the generator 11. If the output signal of the bridge circuit 3 increases, the integrator will also increase the rate of accumulation, and hence the reset frequency of this voltage, i.e., the bridge circuit signal is converted to a frequency.

Claims (2)

The inputs n of the comparators 14-16 receive a variable signal from the output of amplifier 4, the level of which depends on the measured parameter of the sensor. This 65 signal is compared at the inputs n of the comparators with a constant signal supplied to each comparator from the deLite) A circuit having a h output, depending on the signal level of the instrument 4, triggers one or another comparator. The position of the comparators through the formers 18-20 determines the division ratio of the controlled frequency divider 21. As can be seen from the timing diagram (Fig. 2d), when the output switches to the integrator yarn through zero when the input signal is negative at interval t the comparator output is formed by the positive edge of point B, and on the interval t the transition of the integrator output voltage through zero at a positive input signal forms the negative front of point G. Therefore, the task of the driver is to form the same (for example, negative when the integrator goes through zero) At both intervals t, .2, both the input of the imager is given a signal from point B, and to the other - the voltage from the output of the comparator. At an interval c, the signal from point B is positive, and the comparator at a zero forms a positive front. At intervals ta, the comparator outputs a zero signal, positive signals arrive at both inputs of the matching element 23, and a positive signal arrives at both inputs of the matching element 25, and a positive signal at the output (fig.2d). one . At the beginning of the intervals t, one of the inputs of element 23 goes through the inverter 22, and element 25 plus then a positive input to both inputs of element 26 and a negative front is formed at the output of element 26 (Fig 2d). In the interval t the signal of point B is negative, and the comparator at the time of the transition of the integrator through the NL forms a negative front. At intervals t, the comparator outputs a positive signal, a positive signal is received at both inputs of element 25, and zero at both inputs of element 23, plus 26 at the output of element 26. In the beginning of the intervals tt, one of the inputs of the element 23 comes plus through the inverter 22, and the element 25 has a zero then a positive edge is fed to both inputs of the element 26 and a negative front is formed at the output of the element 26 (Fig.2l). The algorithm of operation of the formers is that if at the inputs of, for example, shaper 18, the signals are opposite (zero and plus or plus and zero), the output at the output corresponds to a plus. With the same signals (both pluses or both zeros), the output signal will be zero. The advantage of the invention in comparison with izestnoe is to increase the accuracy and resolution by increasing the dynamic range of output frequencies. Claim 1. Device for converting a bridge sensor signal into a frequency comprising a bridge circuit, a frequency generator whose output is connected to the first input of a matching element and a counting trigger input, the output of which is connected to a second input of a matching element and a control input of a key, which by its information the input is connected through the first resistor to one of the vertices of the power diagonal of the bridge circuit, and the output of the key is connected via an integrator to the input of the main comparator, as well as an amplifier whose output o is connected via the second resistor to the integrator input, and the amplifier outputs are connected to the measuring diagonal of the bridge circuit and the power source, whose output is connected via a switch to the bridge circuit, in order to improve the accuracy of the conversion, n +1) shapers, n comparators, controlled frequency divider and voltage divider with p outputs, the inputs of which are connected to the diagonal of the bridge circuit power, and n outputs connected to the first inputs of additional n comparators s, the second inputs of which are interconnected and with the output of the amplifier, and the outputs of the n comparators are connected to the first inputs of the n drivers, the other inputs of which are interconnected with the first input of the (n + 1) -th driver and the top of the diagonal of the bridge power supply, The shaper units are connected to the control inputs of the controlled frequency divider, the counting input of which is connected to the trigger output, and the output is connected to the control input of the switch, while the second input of the (n + 1) -th driver is connected to the output of the main about the comparator, and the output with a set trigger input. 2. The device according to claim 1, characterized in that - each driver is formed by two inverters And three elements of coincidence, the first element of which is connected to the first input of the driver and the first input of the second coincidence element by the first input through the second inverter connected to the second input of the imaging unit and the second input of the first element of the match, and the output. the two 7 first 1 & match elements are connected to the strokes of the third matching element, the output of which is the output of the driver; Sources of information taken into account in the examination 0 1. Express information Devices and elements of automation and computer technology. 1974, No. 47, p. 5-9. 2. USSR author's certificate according to the application No. 2597412, cl. H 03 K 13/20 ,, 08/31/78.