SU731317A1 - Non-electric value measuring device - Google Patents

Description

measurement method, the essence of which is that during one power pulse, not one is produced, as in a conventional pulse measurement, but two successive measurements of the output signal, followed by subtraction from the second result of the first and then the resulting difference from the first signal. The device works as follows. When the device is turned on, the starting pulse triggers a generator of power pulses, which produces power pulses of duration t, with a definite frequency of follow-up, entering the measuring circuit. In the measuring circuit, a transient occurs due to the heating of the primary resistive converter by the measuring current. At the same time, a starting pulse triggers a generator of paired pulses, the first pulse of which includes a digital measuring transducer, which makes the first measurement of the output signal. The result of the measurement enters the memory cell of the computing unit. Next, the pair of pulses generator repeatedly turns on the digital measuring converter, which performs the second measurement of the output signal of the measuring circuit, the result of which is fed to the computing unit. The computational unit subtracts the first measurement result from the second measurement result, and the resulting difference subtracts the measurement result from the first measurement result. The heating of a resistive converter for an arbitrary number of periods of power supply pulses can be described by the expression G "(+ - (+ 1 I 1 -exp (-. / Then) exp (-t / then) exp () - exp (-t / Chr ) (-T / TO) X (- Ao))

a) temperature of the resistive converter;

6 - measured temperature of the medium;

Р - power dissipated by sensor;

K is the sensor scattering coefficient;

and is the duration of the feed pulse;

/ n - pause time between two

impulses;

 () is the period of pulse generation;

The resulting warming up in quasi-established mode can be reduced to the minimum steady-state transient temperature of the Gmin. mouth ..

Claims (3)

Thus, when measuring the temperature by the difference-extrapolation method and choosing the temporal ratio in accordance with expression (5), the maximum systematic error is determined not by the maximum, as in the usual pulsed measurement method, but by the minimum steady-state transient temperature and varies from 0 to zero the repetition period to Tmin in quasi-established mode at. n is the number of periods of pulse following; That is the thermal constant of the sensor time; t is the time counted from the beginning of each pulse. With a large number of pulse repetition periods n, with constant or slowly changing environmental conditions, a quasi-steady state occurs in the sensor circuit (the state of dynamic equilibrium). In this case, the heating temperature of the converter will be in the temperature range from Hmcn to Gmax, defined by the expressions T + - X - max - G 1-exp - „/.o) e (/) L 1-exp (-t / Cho) + x exp (- n / i: o) -exp (-t; -o) The difference between the established temperature of the resistive converter is measured by the ambient temperature (Gmax-9) and is in this case the maximum systematic result associated with its warming up. In the described device, after two measurements of the duration "i" at the beginning and end of the supply pulse and the calculation, the measurement result for the state of dynamic equilibrium will be determined by the expression max (s) max (s) H x exp (-) - exp (- g / hr) I exp (-T / That))}. (4) () -pr (At a certain ratio between and and ta + exp (-. O) For measurements, the time of the first measurement / and is counted from the beginning of the measurement until its end by the digital measuring converter. In general, it should be selected as the possible conversion time depends on its speed.The duration of the power supply pulse is in accordance with the expression (5) as 4: g: t „np12eXp (,) - 11. (6) The time shift between the beginning of the first and second measurements is equal to s, t i.e. the end of the second measurement cycle, taking into account Flux fluctuations should coincide with the end of the supply pulse. The presence of a pair of pulses in the device favorably distinguishes it from the prototype, as it allows to increase the accuracy of temperature measurement. to the measuring circuit connected to the power pulse generator, a digital measuring transducer connected to the measuring c A computational unit, characterized in that, in order to increase the measurement accuracy, a generator of paired pulses is introduced into it, the input of which is connected to the input of the generator of power pulses, and the output - to the control input of the digital measuring converter. Sources of information taken into account in the examination of 1.Turchin A.M. Electrical measurements of non-electrical quantities. M.-L., “Energie, 1966, p. 135. 2. USSR author's certificate number 247558, cl. G 01 K 1/20, 07.07.67. 3. Hurt, Rucker, Minn COMPUTER in the temperature measurement system by periodic interrogation of sensors. “Electronics, vol. 46, No. 24, 1973, p. 50-57 (prototype).