SU983557A1 - Method and device for measuring physical values changing in time - Google Patents

Description

The invention relates to measuring equipment and is intended for analog measurement of time-varying physical, mainly electrical, quantities.

A known method of analogue measurement of physical quantities, in which the measured value is compared with a reference, and the measured value of "· _ value is judged by the reference value 'and the difference between the measured and reference values, and a device for its implementation, containing the source. reference voltage, an exemplary divider and switching circuit, in it each meter channel is sequentially disconnected from the signal source and connected to the calibrator using a step finder £ 1].

The disadvantage of the meter is the low dynamic accuracy of the measurements.

There is also known a method of analog measurement of time-varying physical quantities, based on the replacement method, which consists in recording the main reference and recorded signals one by one and determining the recorded value from the main reference value and the ratio of recorded signals, and a device for its implementation, containing an amplifier, to the input of which the sources of the measured and main reference signals are connected through attenuators, an analog recorder controlling the input of which is connected to the first output of the trigger unit, the control inputs of the sources of the reference and measured signals are connected to the second and third outputs * of the trigger block [2J.

However, this meter also does not have a sufficiently high dynamic accuracy of measurements.

The aim of the invention is to increase the dynamic accuracy of measurements.

S 983557 4 ⁴

This goal is achieved by the fact that according to the method of analog measurement of time-varying quantities based on alternating recording of the main reference 5 and the recorded signals and determining the recorded value from the main reference value and the ratio of the values of the recorded signals, an additional reference value is selected that varies in time similarly measured and opposite in phase, add this value to the measured, and the measurement result is determined as the sum of the recorded and * ⁵ additional reference values.

Moreover, the device for implementing the method, comprising an amplifier, the input of which is connected to the outputs of two attenuators connected by its own 20 inputs respectively to the outputs of the sources of the measured and main reference signals, the measuring input of the analog recorder is connected to the output of the amplifier, the input of which is controlled 25 connected to the first output of the launch block, the control input of the main reference source is connected to the second output of this block, and the control input of the measured -signal source is connected to the third output, sn It is indicated by an additional reference source, the control input of which is connected to the third output of the launch unit, and the output - with the output of the mains of ₃₅ reference source.

In FIG. 1 shows a structural diagram of a device; in FIG. 2 is a recording chart of a measured exponential signal. ₄₀

The device contains an amplifier 1, the output of which is connected to the measuring input of the analog recorder 2. An output of the amplifier 1 through the attenuator 3 is connected to the output of the source _{45 of the} 4 measured signal, and through the attenuator 5 “the outputs of the main 6 and 7 additional reference sources. 'The control input of the analog recorder 2 is connected to the first output start block 8, to the second output of this unit is connected the control input of the basic reference source 6, and the third - the control inputs of the additional source 7 and the reference source 4 ⁵⁵ Nala The signal measured.

The method is as follows.

When the control signal arrives from the start unit 8 at the time -4 ^ (Fig. 2), the broaching mechanism of the analog recorder 2 is turned on. Then at time 4, ^ the main reference source 6 is turned on, the signal 9 from which passes through the attenuator 5 and amplifier 1 to the recorder 2. After the end of signal 9 during the time t ^ -t ^ zero values are recorded. At the time point, the trigger unit 8 simultaneously includes a measured voltage source 4 and an additional reference source 7- Signals 10 and 11 of sources 4 and 7 coincide in shape and are opposite in phase (Fig. 2, dotted line). These signals are algebraically summed at the input of amplifier 1, and the addition result (signal 12) is recorded by block 2. Signals 12 and 9 should be comparable in amplitude. The relative magnitude of these signals is set by attenuators 3 and 5.-Since the main and additional reference sources 6 and 7 are connected to amplifier 1 through a common attenuator 5, their voltages must be close or equal in magnitude. The measured value (for example, electric voltage) is determined by the expression ^l W ^and p ⁺ where Pr is the voltage being detected;

U is the voltage of an additional 9DOP _reference source.

In a particular case, when measuring a pulse of an exponential shape, the measured voltage at a time is determined by the expression ^ IOSnb ^ RB ^ edoPb ^{1 and} _ 4 ^ + ϋ p fteosn ^and edop ^e / where II is the voltage of the main standard of the main source;

U - additional voltage

EDopBetalonny source at time point 4 ^;

U is the amplitude value of the voltage ^E <A ^{OP of the} additional source;

h is the amplitude of the main reference signal 9;

h is the value of the recorded 2-signal 1-2 at the time-time. HMig-;

- exponent of the measured signal;

L ~ ^ P ^{shaft integral} time between the measuring instants, and including an additional reference source.

In the particular case when U ^^ Up = 0 and the dynamic measurement error is generally absent regardless of the inertia of the meter. When measuring by the known method = Up and the absolute measurement error is equal. In measurements by the proposed method, the absolute error of measurement of the recorded value of signal 12 is » ^P P ^And this cGx <cQ - The relative dynamic error of the measurement result decreases in proportion to the ratio of the amplitudes of the signals A and 12 V — for

The measured signals vary according to the law of the decreasing exponent, the exponent is <= C = 20 1 / C, the measurement time is 0.040 s.

The static error of the meter is determined by the intrinsic noise of the element / ^{5 of the} amplifier and in the frequency range 0-60 Hz is 1 (Γ ^έ V, which corresponds to the reduced error of 1%. Dynamic error of measurements taken 5 * 7 · 1s after the signal is turned on (start wind tunnel), is составляет 2%. For large times, the dynamic error decreases, but due to a decrease in the measured signal, the relative static measurement error increases.

The invention requires little gauge improvements and allow a decrease ^{of 40.} sew dynamic measurement error not less than 2 times. This is because the attenuation attenuation coefficients of the meter are multiples of two and the measured and additional reference signals differ no more than 2 times

Claims (2)

The invention relates to a measurement technique and is intended for analog measurement of time-varying physical, preferably electrical, quantities. The known method of analog measurement of physical quantities, at which the measured value is compared with the reference, and the value of the measured value is judged by the reference value and the difference between the measured and reference values, and the device for its implementation, containing the source. a reference voltage, an exemplary divider and a switching circuit, in which each channel of the meter is sequentially disconnected from the signal source and connected to the calibrator with the help of the step finder 1. The disadvantage of the meter is s low dynamic measurement accuracy. There is also known a method of analog measurement of time-varying (Jw zic values based on the replacement method, which consists in alternately recording the main reference and recorded signals and determining the recorded value from the main reference value and the ratio of the recorded signals, and the device for its implementation containing an amplifier, to the input of which sources of measured and main reference signals are connected through attenuators, an analog recorder connected to the amplifier output The input of which is connected to the first output of the start-up unit, the second and third outputs of the start-up unit are connected to the control inputs of the sources of the reference and measured signals 2. However, this meter also has a very high dynological degree of measurement accuracy. The aim of the invention is to increase the dynamic measurement accuracy 398 The goal is achieved by the fact that, according to the method of analog measurement of time-varying bieic values, based on the sequential recording of the main reference and recorded with and determining the recorded value by the main reference value and the ratio of the values of the recorded signals, an additional reference value varying in time is chosen analogously measured and opposite to it in phase, this value is added to the measured value, and the measurement result is determined as the sum of the recorded and additional reference values. The device for carrying out the method, containing an amplifier to the input of which the outputs of two attenuators connected by their inputs respectively to the outputs of sources of measured and main reference signals are connected, to the output of the amplifier is connected the measuring input of the analog recorder, the control input of which is connected to the first output of the trigger unit , the control input of the main reference source is connected to the second output of this block, and the source of the measured signal is connected to the third output; an additional reference source, the control input of which is connected to the third output of the trigger unit, and the output - to the output of the main reference source. FIG. 1 shows a block diagram of the device; in fig. 2 - registration diagram of the measured exponential signal. The device contains an amplifier 1, to the output of which the measuring input of the analog recorder 2 is connected. The input of the source k of the measured signal is connected to the input of amplifier 1, and through the attenuator 5 - the outputs of the main 6 and additional 7 reference sources Control input of the analog recorder 2 is connected to the first output of start block 8, the control output of the main reference source 6 is connected to the second output of this block, and the control inputs of the additional reference source 7 and source 4 are connected to the third output. zmer emogo sig Nala. The method is carried out as follows. When the control signal arrives from the start block 8 at time t (Lig. 2), the analog recorder 2 pulls in. Then, at the time Ln, the main reference source 6 is switched on, the signal is sent from which through an attenuator 5 and amplifier 1 is fed to recorder 2. After the termination of signal 9, zero values are recorded over time. At time t /, the start block 8 simultaneously switches on the source ij of the measured voltage and the additional reference source 7. The signals 10 and 11 of the sources (and 7 coincide in shape and opposite in. 2, dotted line). These signals are algebraically summed at the input of amplifier 1, and the result of the addition (signal 12) is recorded by block 2. Signals 12 and 9 must be commensurate with amplitude. The relative magnitude of these signals is set by attenuators 3 and 5. Since the main and secondary reference sources 6 and 7 are connected to amplifier 1 through a common attenuator 5, their voltages must be close to or equal in magnitude. The measured value (for example, electrical voltage) is determined by the grinding of% M 9 Wn. 1) where Pr is the recorded voltage, and is the voltage of the additional 9EP reference source. In the particular case, when measuring an exponential pulse, the measured voltage at time t is determined by the expression MOSnb Rb EAopb P (t5-i4) eos EEPA / where and is the voltage of the main reference source; And - the voltage of the additional ° reference source at the moment of time -t and is the amplitude value of the voltage of the secondary source; fi is the amplitude of the main reference signal 9; the value of the recorded signal 1-2 at time. neither; cc is the exponent of the measured signal; bg-t. - the time interval between the moments of measurement and the inclusion of an additional reference source. In the particular case with Up 0 and the dynamic measurement error is altogether absent regardless of the inertia of the meter. When measuring by a known method (.up and the absolute measurement error is equal to D. When measuring the proposed method, the absolute measurement error of the recorded signal value 12 is L2 at that (Go cC |. The relative dynamic error of the measurement result decreases proportional C1 to ratio of signal amplitudes .: 11 and 12 times. Weighted variable signals change according to the law of a falling exponent, exponent ct 20 1 / С, measurement time O, p. Static meter error is determined by its own and 11ums of an elec- tron amplifier and in the frequency range O-bo Hz is 1 (G V, which corresponds to a reduced error of 1. The dynamic error of measurements taken 5–7. after turning on the signal (starting an aerodynamic cable) is 1012 %. At longer times, the dynamic error decreases, but due to a decrease in the magnitude of the measured signal, the relative static measurement error increases. The invention requires a slight refinement of the meter and will allow to reduce the dynamic error rhenium not less than 2 times. This is due to the fact that the attenuation coefficients of the meter attenuators are a multiple of two and the magnitudes of the measured and additional reference signals differ by no more than 2 times. Formula 1. Analog measurement method of time-varying physical ones. 9 76 values, based on the sequential recording of the main reference and recorded signals and determining the recorded value from the main reference value and the ratio of the signs of the recorded signals, characterized in that, in order to increase the dynamic accuracy of measurements, an additional reference value is chosen that varies in time. phase opposite to it, add this value to the measured one, and the measurement result is determined as the sum of the register and additional reference values. 2. An apparatus for carrying out the method according to claim 1, comprising an amplifier, to the input of which two outputs of two attenuators connected to the outputs of sources of measured and main reference signals are connected, to the output of the amplifier is connected a measuring input of an analog recorder, control the input of which is connected to the first output of the start-up block, to the second output of this block is connected the control input of the main reference source. to the third, the control input of the source of the measured signal, characterized in that, in order to increase the dynamic accuracy of the measurement, it is equipped with an additional reference source, the control input of which is connected to the third output of the trigger unit, and Bbi inlet to the output of the main reference source. Sources of information taken into account in the examination 1 of the USSR Author's Certificate No. 185) 078, Yu1. (niR 35/00, 1966, 2. Kuzmin A.I. Sixteen-channel system for measuring heat fluxes in hypersonic wind tunnels - Collected Works of TsAGI, Issue 1683, 1976, 1