SU441521A1 - Measuring device for sawtooth voltage non-linearity - Google Patents

Description

one

The invention relates to the field of electrical measuring equipment and can be used in instrumentation to check pre-saw saw voltage and current generators, in measuring the speed of electrical processes, in equipment for controlling the shape of signals, in automation systems.

By bus. St. 335618 A sawtooth voltage nonlinearity measuring device is known, comprising an adjustable delay line, a sawtooth voltage generator connected in series, a differentiation unit, a switch, a filter, a voltage – time converter, and an oscilloscope. The oscilloscope is connected to a voltage converter — time directly, and to a switch through an adjustable delay line.

However, such a device has a significant error in measuring the sawtooth voltage.

The purpose of the invention is to reduce the measurement error.

This is achieved by the fact that the proposed device is equipped with a memory circuit and an additional adjustable delay line connected between the sawtooth generator and an additional delay line, the memory circuit being connected between the threshold circuit and the filter.

The voltage at the filter output varies in accordance with the expression

U, (t) U7, -Kof, (1)

where f / 7 is the voltage at the filter output; (70) the voltage at the output of the filter at the moment of arrival of a pulse from the output of the threshold circuit (this moment coincides with the moment of interrogation of the switch);

/ C - the rate of decline (or increase)

stress uj due to

leakage and constant time

filter;

ti is the time interval from the moment the switch was polled to the time when the voltage-converter started up.

When measuring nonlinearity in a known device, it is necessary to change the switch polling delay time with a variable delay line. This means that the time interval ti between the switch polling emulsion and the voltage-pulse start-up pulses varies accordingly. The longest time interval between the indicated pulses is equal to the working stroke T of the saw-tooth process from the output of the measurement object. Thus, the drop (or rise) of the voltage at the output of the DC filter is equal to W, / C T. (2) Since any change in voltage at the filter output is recorded as a signal that the object sawtooth process is non-linear, the value of Ari causes a measurement error equal to AC. L - //: / С „А /,: / SP / SU G. (3) where Ln is the scale factor of the parameter measuring device i, Value (the smaller, the smaller / (and and G. The value of C depends on the filter properties In order to reduce the measurement error, the proposed device is equipped with a memory circuit and an additional adjustable delay line switched on with a sawn voltage generator and an additional delay line, the memory circuit being connected between the threshold circuit and the filter. During the measurement process in this device, the interval between the polling pulse and mutator and starting the voltage converter — the time remains unchanged, which is ensured by running the measurement object through a variable delay line and interrogating the switch through a constant delay line.Figure 1 shows a block diagram of the measuring device, where 1 is the measurement object; 2 —differentiated circuit; 3 — amplifier; 4 — threshold circuit; 5 — oscilloscope; 6 — switch; 7 — constant-force filter; 8 — voltage-time converter; 9-variable delay line; 10 - constant delay line; 11 is a memory diagram. FIG. 2, a – d, shows time diagrams for the operation of the proposed device, where a is a saw-tooth process from the object's output; b - synchronization pulse from the oscilloscope output; в - impulse at the output of the threshold circuit; d is the voltage from the filter output; d - impulse from converter output - time. The moment of launch of the object 1 relative to the synchronization pulse (Fig. 2, b) depends on the delay time tg {Fig. 2, a) a variable delay line (in Fig. 2 two cases are shown: when ig-O is a continuous line and when is a dashed line). The switch is polled at a time determined by the value of a constant delay line. This time should be equal to the time G of the working area of the saw-tooth process. Voltage converter - time triggered by a synchronization pulse (Fig. 2.6). The peculiarity of the device is that the movement of the interrogation (sampling) moment of the switch within the fork-like process is carried out not by changing the interrogation moment of the switch with respect to the synchronizing pulse, but by changing the moment of launching the object relative to the synchronization pulse. In addition, a memory circuit is introduced in the device for storing the amplitude of the pulse from the output of the threshold circuit. This increases the sensitivity of the meter in Г „/ Т4 times (Г„ is the period of the synchronizing pulse, Т4 is the pulse duration from the output of the threshold circuit) in comparison with the known device. Consider two cases. First, when the sawtooth process is perfectly linear. In this case, a change in the delay tg does not lead to a change in the amplitude of the pulse (Fig. 2, c), since, after differentiation, the linearly varying voltage (Fig. 2, a) by circuit 2, a constant level is obtained in the portion of the signal travel. Obviously irrespective of the value of tg, the nature and magnitude of the voltage (Fig. 2, e) from the output of filter 7 are constant (for any conditional moment measured from the moment of interrogation of switch 6). Since t. (Fig. 2, d) is constant and does not depend on the value of ig, from equation (1) it follows Af / 7 0, i.e. the change in pulse t (Fig. 2, () The device registers (without taking into account the resolution). The second case is when the saw-tooth process is non-linear. After differentiating at section T from the output of circuit 2, a non-constant level is obtained. the circuit and the filter (Fig. 2, c) change the value of -m (Fig. 2, c) by Am, that d) by the values of At / 4 and A Uj. The value of m (Fig. 2, d) is changed by At, which fixes the oscilloscope. Mathematically, from equation (1) we get W, W7, + D / SU t ,. The first term of equality (4) is due to the nonlinearity of the process under study, the second is the dependence of YI on the voltage level. The differences of the proposed device are clearly seen if we consider the total differential from C / t from equation (1) df /, dUi, - dKu t, - K d /, (5) final increments A, - Af / 7, - A / C - Co A, (6) Like in the proposed device t const, which is Co A, O, (7) then expresses the essence of the invention. The component / C is the instrumental error of the known device that limits the accuracy of measurements, since the proposed device does not have this error of 0, thereby improving the measurement accuracy if the CCr is the main component of the total error. The subject invention The measuring device of non-linearity sawtooth voltage, dependent on the author. St. No. 335618, characterized in that, in order to reduce measurement error, it is provided with a memory circuit and an additional adjustable delay line connected between the sawtooth generator and an additional delay line, the memory circuit being connected between the threshold circuit and the filter.