RU2309415C1 - Device for measuring capacitance of capacitive pickup - Google Patents

Abstract

FIELD: measuring technique.

SUBSTANCE: device can be used in measuring aids for measurement and checking of non-electric values by means of capacitive pickups. Device for measuring capacitance of capacitive pickup has microcontroller, digital indicator, and oscillator. Measured capacitance capacitive pickup is connected with time-setting circuit of oscillator. Output of oscillator is connected with counting input of microcontroller's counter. One of outputs of microcontroller is connected with generation resolution input of oscillator. Pulse-width modulator filling-up factor converter is brought into device additionally as well as integrating RC-circuit. Output of pulse-with modulator of microcontroller is connected with inputs of integrating RC-circuit and output of pulse-width signal/digital code modulator. Output of the latter is connected with digital indicator. Digital and analog signals can be formed at output of device.

EFFECT: widened functional abilities.

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Description

FIELD OF THE INVENTION

The invention relates to measuring equipment, in particular to devices for measuring the capacitance of capacitor sensors, and can be used in means for measuring and monitoring non-electric quantities by capacitor sensors.

State of the art

A device for measuring electric capacitance is known, comprising two single-vibrators connected according to a circular oscillator circuit, two integrating RC links connected to the outputs of the corresponding single vibrators, an indication unit connected between the outputs of the integrating RC links, capacitors, respectively, of the standard capacitance, are included in the timing chains of the single vibrators and measurable. A constant voltage is formed at the output of the device, the value of which depends on the change in the measured capacitance and which is reflected by the indicating unit (see US Pat. RF No. 2156472, class G01R 27/26).

The disadvantages of the known solution are limited functionality — only an analog signal is generated at the device output and there is no digital signal.

A digital device for measuring capacitance and its deviation from the nominal value is known, which contains the first and second generators, capacitors of the measured capacitance and reference capacitor are included in the oscillator circuit, the outputs of the generators are connected to a device that generates pulses with a repetition frequency equal to the frequency difference of these generators, differential frequency pulses arrive at the key, which is controlled by the frequency divider of the pulses coming from the first generator, the pulses from the key output go to the counter IR for generating a binary code proportional to the measured capacitance (see ed. St. No. 331340, class G01R 27/26).

A disadvantage of the known solution is limited functionality — only a digital signal is generated at the device output and there is no analog signal.

The closest in technical essence to the claimed technical solution and adopted by the authors for the prototype is a device for measuring non-electric quantities by capacitor sensors, containing a microcontroller, a digital indicator and two generators, a capacitor sensor of the measured capacitance and a model capacitor are included in the timing circuits of the generators, the outputs of the generators are connected to counting inputs, respectively, of the first and second counters of the microcontroller, one of the outputs of the microcontroller is connected to I give permission both generators generating a digital indicator connected to one of ports of microcontroller (see. US Pat. RF №2214610, cl. G01R 27/26).

A disadvantage of the known solution is limited functionality — only a digital signal is generated at the device output and there is no analog signal.

Disclosure of invention

The technical result that can be achieved using the present invention is to expand the functionality of the device, namely, at the output of the device, digital and analog signals are generated.

The technical result is achieved by the fact that in the device for measuring the capacitance of a capacitor sensor, containing a microcontroller, a digital indicator, a generator, during which the capacitor sensor of the measured capacitance is connected, the generator output is connected to the counting input of the microcontroller counter, one of the outputs of the microcontroller is connected to the generation permission input generator, a converter of the duty cycle of the pulse-width modulator signal into a digital code and an integrating RC link, introduced m to the output of the pulse-width modulator of the microcontroller are connected the inputs of the integrating RC-link and the converter of the duty cycle of the signal of the pulse-width modulator into a digital code, to the output of which a digital indicator is connected.

As a device with an analog input, either an automatic regulator with a unified analog voltage input or an analog-to-code converter can be used to control a linear scale on semiconductor light-emitting diodes.

The drawing shows a structural diagram of a device for measuring the capacitance of a capacitor sensor.

The implementation of the invention

A device for measuring the capacitance of a capacitor sensor contains a generator 1, a microcontroller 2, an integrating RC link 3, a converter 4 for the duty cycle of the pulse-width modulator into a digital code and a digital indicator 5. The output of the generator 1 is connected to the counting input of the counter of the microcontroller 2, one of the outputs microcontroller 2 is connected to the generator enable enable input 1. During the drive circuit of generator 1, a capacitor sensor Cx is connected, the capacitance of which must be measured. An integrating RC link 3 and a converter 4 are connected to the output of the pulse-width modulator of the microcontroller 2, and a digital indicator 5 is connected to the output of it.

A device for measuring the capacitance of a capacitor sensor operates as follows.

Microcontroller 2, at the beginning of each measurement cycle, sets the logic voltage level that allows generation at the resolving input of generator 1 and starts two internal counters, the first of which is used to count the pulses of generator 1, the second counter - to count the clock pulses of the internal generator of microcontroller 2. When the first counter is full, the microcontroller 2 stops the second counter, in which the binary code N is formed by this moment. The binary code N is proportional to the change in the capacitance Cx Athorne sensor and is defined as follows:

N = mT1 / T2,

where m is the number of periods of the generator 1, counted by the first counter, is set by software, which allows you to control the resolution of this measuring device; T1 - the period of the rectangular pulses of the generator 1, is determined by the expression T1 = kCx, where k is a coefficient characterizing the properties of a particular generator circuit and having a dimension of resistance; Cx is the measured capacitance of the capacitor sensor; T2 - the repetition period of the clock pulses of the internal oscillator of the microcontroller 2, operating from a quartz resonator.

The microcontroller 2 outputs to the input of the integrating RC link 3 and to the input of the converter 4 a pulse width modulator (PWM) signal. The duty cycle of the PWM signal is proportional to the value of the N code. A code is supplied from the output of the converter 4 to the input of the digital indicator 5 to display the measured capacitance in decimal form. The voltage at the output of the integrating RC link 3 is proportional to the duty cycle of the PWM signal, and therefore to the change in the measured capacitance Cx.

Capacitor sensor, generator 1 and microcontroller 2 can be placed in one housing, directly near the object of control. The information signal from the PWM output can be transmitted, over a single signal wire, over long distances, several tens of meters.

You can connect either an automatic controller to the output of the integrating RC link, to the input of which you need to supply a unified signal (voltage or current), or an analog indicator, or a linear LED indicator, which is controlled by a microcircuit, for example K1003PPZ.

The invention in comparison with the prototype and other known solutions has the following advantages:

- the possibility of simultaneously receiving signals of analog and digital form;

- Information can be transmitted over long distances through only one signal wire.

Claims (1)

A device for measuring the capacitance of a capacitor sensor, containing a microcontroller, a digital indicator, a generator, during which the capacitor sensor of the measured capacitance is turned on, the output of the generator is connected to the counting input of the counter of the microcontroller, one of the outputs of the microcontroller is connected to the generator generation enable input, characterized in that it introduced a converter of the duty cycle of the pulse-width modulator signal into a digital code and an integrating RC link, and to the output of the latitudinal On the O-pulse modulator of the microcontroller, the inputs of the integrating RC link and the converter of the duty cycle of the pulse-width modulator into a digital code are connected, to the output of which a digital indicator is connected.