SU1195291A1 - Capacity-to-time interval converter - Google Patents

Abstract

The invention relates to electrical measuring technology and can be used in measuring devices and systems, for example, in good meters. The purpose of the invention is to expand the functionality of the converter. The converter consists of a series-connected oscillatory circuit 1, an amplifier 2, a detector 3, an extremum extraction unit 4, a trigger 5, as well as a series-connected functional converter 6, a sawtooth source 7, a control unit 8, and also a high-frequency generator 9, sources voltage offset-. neither 10, key 11, isolation elements 12 and 13, the capacitance 14 being converted. The oscillatory circuit is formed of a capacitor inductance coil and a chain with a sequence. It is suitable for the included capacitor and varicap. The capacitor of this chain separates the constant component of the varicap and source 10. 2.I.L. , (L

Description

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This invention relates to electrical-diecasting technology and can be used in measuring devices and systems, for example, in goodness measurements.

The purpose of the invention is to expand the functional capabilities of the converter. .

FIG. 1 shows a functional converter circuit; in fig. 2 - block diagram of the control unit.

The converter consists of a series-connected oscillatory circuit 1 (measuring two-pole), amplifying 2, detector 3, extremum extraction unit 4, trigger 5, a. also connected in series functional converter 6, sawtooth source 7, control unit 8, a. also from the view / frequency generator 9, the bias voltage source 10, the key 11, the junction terminals 12 and 13, the capacitance 14 being converted.

The composition of the oscillating circuit includes an inductor, a capacitor and a chain with a series-connected capacitor and varicap. The capacitor of this chain is used to separate the constant component of the varicap and the source of the bias voltage. The bias voltage source 10 serves to set the required DC mode when measuring the varicap capacitance and does not affect the operation of the converter when measuring the capacitance. capacitors.

Uncoupling elements 12 and 13 are used to isolate DC and AC voltage circuits.

In the outgoing state at the terminals there is no convertible capacity. The high frequency generator 9 generates a sinusoidal voltage that is applied to the oscillating circuit 1. At the output, the sawtooth source 7 acts. sawtooth voltage. This is a voltage. is fed to the functional converter 6, from the output of which the varying voltage is applied to the varicap of the oscillatory circuit. With a minimum Variable Voltage on the Varicap, the latter has a maximum capacity and the circuit is tuned. in resonance. A sinusoidal voltage is fed from the circuit to the input of amplifier 2, and its output is to detector 3. Next, the detected bell-shaped voltage is fed to the input of the extremum extraction unit 4. The latter produces a voltage pulse at the time of the input signal's extremum. The pulse from the output of block 4 is fed to the separate input of the trigger 5,

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When measuring the capacitance (capacitor or varicap) 14, it is connected to the terminals

converter

As in the first case, the sawtooth voltage is fed to the input of the functional converter 6. The functional converter forms from the sawtooth voltage a bias voltage UCM () which is applied to

) 0 contour. The functional converter generates a clock voltage so that the capacitance of the varicap oscillating circuit has a linear dependence on time. As a functional converter

15, a piecewise linear approximator may be used. The capacity of the varicap oscillating circuit varies according to the law

, Ce .Kt,.

where c | - the capacity of the oscillatory circuit, 20. at which the resonance occurs

at the operating frequency .; .

K is the steepness of the change in the capacitance of the varicap oscillating circuit, a constant value ;.

25 t is the time, О t T, where T is the duration of the saw voltage. When a bias voltage is applied to the varicap of the oscillating circuit, the latter changes the value of its capacitance from the maximum value to the minimum value.

With the arrival of a varying voltage on the varicap of the oscillating circuit, the latter periodically tunes into resonance with the frequency of the incoming variable voltage. . If the resonance moment in the circuit is without a convertible capacitance i, but with a convertible capacitance 2, then the varicap capacitance is an oscillator. the circuit changes to a value equal to the magnitude of the capacitance conversion

.) Cx

or

 .0)

where k is the slope of the change in the capacitance of the varicap oscillating circuit constant n. by value.

From (1) it follows that the measured capacitance

proportional to the time interval ui

The change in the bias voltage at the output of the functional converter 6 starts from the level at which circuit 1 without measured capacitance 14 is tuned to resonance. The start of the bias voltage change is synchronized via the sawtooth source 7 by the control unit 8, which sets the trigger 5 at this time 55 () to one state. When measured capacitance 14 arrives at the measurement positions, when the circuit is tuned to resonance (time i), the output of the extremum recovery unit 4 takes a pulse that will reset trigger 5 to another state. If there is capacitance 14, the process of generating the triggering impulses 5 repeats cyclically. At the output of the trigger 5 will act impulses duration Ai, i.e., proportional to Su. At the moment of time (tj ti) at the generator output, the sawtooth voltage will be a voltage, proporodonal C, which is supplied through the key 11 to the second output of the device, the key is controlled by the output pulse of the unit. Therefore, the converter allows to obtain two electrical signal parameters pulse duration and voltage, which are proportional to the measured capacitance Cj (which determines its wider functionality. The control unit (Fig. 2) contains a pulse generator 15 and a delay unit 16. The output of the pulse generator s connected to the input gene Rhatore pulse delay unit. The output of the pulse generator is supplied furthermore to the input source voltage ramp 7 and output from the delay unit 5 corresponding trigger input.

Claims (1)

HaffHH W 914 Formula of the invention A capacitance-to-time converter containing a capacitive sensor included in a measuring two-port network. with modulated parameters, high-frequency generator, an extremum extraction unit, a trigger, a key, the input of the extremum extraction unit connected to a two-terminal through serially connected amplifier and detector, and its output to one of the trigger inputs, the output of which is connected to the control input of the key, characterized in that, in order to extend the functionality, sequentially connected control unit, sawtooth generator, functional converter and voltage source are introduced into it the offset, the output of the sawtooth generator is connected to the operating input of the key, and the output of the functional converter is connected via an isolator to the varicap measuring two-pole, and the control input of the switch is connected to the output of the extremum extrusion unit and the trigger input, the output of the bias voltage source is connected Isolation element with a clamp to connect the measured capacitor, the temporary output of the converter is the trigger output. flOf / e. 2