SU1168874A1 - Variable-capacitance transducer - Google Patents

Abstract

1. CAPACITOR TRANSMITTER, containing two one-shot, during which drive circuits are connected two sensor capacitors, a clock generator, the first output of which is connected to the input of the first one-oscillator, as well as a filter, which is introduced into it to increase the accuracy of the conversion. a source of two-pole voltage, a switch with three analog and two control inputs, a dividing unit with one analog and two control inputs, the output of a single vibrator connected to the first and second control inputs of the switch and the dividing unit, the source outputs are connected to the analog inputs of the switch, the output of which is connected to the input of the filter, the output of the filter is connected to the analog input of the dividing unit, and the generator has a second inverted output connected to the input of the second one-channel. ra. 2. The converter according to claim 1, characterized in that the dividing unit comprises a differential integrator, a filter, a switch with two control and two analog inputs, the analog inputs of the switch are connected to the output of the differential integrator and a common bus, respectively, the filter is connected between the output of the switch and the inverting input of the differential integrator, the analog input of the division unit is connected to "e" (L the inverting input of the differential integrator, and in the equalizer the inputs of the unit are connected to the control 3.The converter, according to claim 1, is characterized by the fact that the one-shot contains two logic elements 2I-NOT, a key, the first input of the first element being connected to 00 00 by a capacitive sensor, and the second input to the second input BTopioro element and the input of the one-shot, the output of the first 4; ai element is connected to the first input of the second element, the output of which is connected to the output of the one-shot, and the key is connected between the first input of the first element and the common bus, and the control input of the key is connected to the input of the one-shot.

Description

1 The invention relates to a measurement technique, in particular to the measurement of non-electrical quantities using a differential capacitive sensor as a primary transducer. The purpose of the invention is to increase the accuracy of a converter by imparting its type conversion function, p -V 2. Figure 1 shows the functionality of a capacitive converter circuit with the function V -V 1. VK in FIG. 2 are diagrams explaining its operation. The converter contains 1 clock pulse generator, one-oscillators 2, during which drive circuits the differential capacitors (C and C,) of sensor 3 are connected, the source 4 of bipolar voltage switch 5, filter 6 and division unit 7. Single-oscillator 2 contains two logic elements 2I - NO 8, to one of the inputs of which a capacitor of the sensor 3 is connected, a key 9, under a switch parallel to the capacitor, the Dividing unit form a differential integrator 10, a switch 11,. filter 12 connected between the switch output and the inverting input of the differential integrator Device. works as follows. A generator impulse, for example, a direct output (fig. 2a), the key 9 is broken, provides the capacitor charge of the sensor 3 with a linear selection current of the element 2I – NOT. In this case, the one-shot begins to pulse the level of logic O (Fig. 2b), continuing until the voltage on the capacitor is perceived by the valve as logical 1. In the presence of a pulse of the new vibrator, the input of the filter 6 is connected via a A2 to the mutator 5 one polarity, and in its absence - to a common bus (fig.2d). From the moment the pulse generator is removed from the direct output, the capacitance begins to be discharged through the public key, preparing a constant (zero) level for its next charge. At the same time, the emerging pulse of the inverted output of the generator (Fig. 26) performs the above operations for the second one-shot. Filter 6 is averaged (Fig. 2e) over CS durations, {fKCj one-shot voltage ± and „on period T of generator II Uo () UoK () TT Differential integrator 10 of the dividing unit through the feedback circuit switch 11 - filter 12 balances the voltage at its inverting input with the voltage at the non-inverting input (figure 2). 71 to U (, K ™, therefore the converter realizes the desired function of measuring V -V. B-fl-TTGg-1-C, -C) which provides independence from changes in the frequency, dielectric constant of the dielectric. With a tone in addition to ensuring overall linearity of the transfer characteristic for sensor 3 with a linear conversion function of the measured non-particle to capacitance circuit provides a significant linearization of the transfer characteristic when using the sensor with a non-linear conversion function (as a result of dividing the nonlinearity by non-linearity) In addition, the input of the filter 6 is fixed at the reference voltages (tU (j, common bus), so that the converter is insensitive to non-identical levels of single-vibration pulses corresponding to logical 1 and O.

FIG. 2

Claims (3)

1. CAPACITIVE · CONVERTER containing two one-shots, during which two capacitors of the sensor are connected, a clock pulse generator, the first output of which is connected to the input of the first one-shot, and also a filter, characterized in that, in order to increase the conversion accuracy, they are introduced into it a bipolar voltage source, a switch with three analog and two control inputs / division block with one analog and two control inputs, and the outputs of the single vibrators are connected respectively to the first and the second control inputs of the switch and the division unit, the source outputs are connected to the analog inputs of the switch, the output of which is connected to the filter input, the filter output is connected to the analog input of the division unit, and the generator has a second inverted output connected to the input of the second one-shot. 2. The converter according to claim 1, wherein the division unit contains a differential integrator, a filter, a switch with two control and two analog inputs, the analog inputs of the switch connected to the output of the differential integrator and • common bus, respectively, the filter · is connected between the output of the switch and the inverting input of the differential integrator, the analog 'g input of the division unit is connected to the non-inverting input of the differential integrator, and the control inputs of the block are connected to the control odes switch. 3. The converter according to claim 1, characterized in that the single-shot contains two logical elements 2I-NOT, a key, the first input of the first element being connected to. capacitive sensor, and the second input with the second input of the second element and the input of the one-shot, the output of the first element is connected to the first input of the second element, the output of which is connected to the output of the one-shot, and the key is connected between the first input of the first element and the common bus, and the control input of the key is connected with one-shot input. . SU 1168874 1 168874