SU1649308A1 - Device for measuring time constants of physical magnitude sensors - Google Patents

Abstract

The invention relates to technical measurements and improves the accuracy of determining the time constant of sensors of physical quantities and extends the field of application of the device. When measuring the time constant, the sensors 1 and 2 under study are switched on differentially, and the first 4 and second 5 models of sensors with the same transmission characteristics are connected in series to the output of one of the sensors. In the process of a non-stationary perturbation on the sensor inputs, blocks 6 and 7 of adjusting the corresponding models using extreme control minimize the difference between the output signals of the sensors and their models. The magnitude of the signal that compensates for the dynamic mismatch of the signals of sensors 1 and 2 and their models 4 and 5 determine the time constants of the sensors, which are recorded by the first 15 and second 16 recording units. 1 il. g (L o Ј CO SO O O 00

Description

The invention relates to technical measurements, in particular, to devices for determining Indicators of inertia for sensors of varying physical magnitudes directly under the conditions of their use.

The purpose of the invention is to improve the accuracy of determining the constant time of sensors and expanding the scope of application of the device.

The drawing shows a block diagram of the device.

A device for determining the constant time of physical value sensors contains the first and second sensors 1 and 2, the unit 3 measuring the difference of the output signals of the sensors, the first and second models 4 and 5 sensors, the blocks 6 and 7 adjusting the first and second models 4 and 5 sensors, respectively first and sometimes switches 8 and 9, first and second inverters 10 and 11, logic block 12, block 13 for calculating the inverse value adder 14, first and second registering blocks 15 and 16, variable gain amplifier 17, integrator 18 in the negative reverse circuit Amplifier 17, null organs 19 and 20, shapers 21 and 22 of different polarity pulses, an EXCLUSIVE logic element OR 23, counting trigger 24, time interval to voltage converter 25, extremum determining unit 26, subtraction unit 27, block 28 module detection, extremum determination unit 29, adder 30, counting trigger 31 with positive polarity control, counting trigger 32 with negative polarity control logic element AND 33, executive body 34 (of a latch type).

To the inputs of sensors 1 and 2, having respectively the following transfer functions:

W, (P)

f

IT, - P

 HT-TP

where Tj, TЈ are the sought time constants (transfer coefficients without loss of generality are taken equal to one),

the same arbitrary nonstationary perturbation X (t) acts.

The transfer function from this disturbance to the signal difference / 2 (0-

Y "(O and output

unit 3 measuring the difference of the output signals of the sensors is equal to

w / rc T1: T4) .R

vj; (1 + tch. R) - ()

The transfer function of the first 4 sensor model is

five

0

five

0

five

0

five

0

five

T -1

R

where K, - adjustable coefficient

transmission amplifier 17 with adjustable transmission ratio;

one

to;;

- the transfer function of the integrator 18 of the negative feedback circuit of the amplifier 1 7.

The transfer function of the second model 5 sensors is equal to the coefficient K 5 of the amplifier transmission with an adjustable transmission coefficient, i.e. W (P) K5.

The transfer function from X (O to signal) at the input of the model 5 has the form

W6 (p) 47PT

The operation of the device is based on the similarity of the transfer functions W (P) and

Wg (P) and occurs in three stages.

At the first stage, the correlated signals Yj (t) and the difference CYa (t) - (O so that depending on the ratio of the unknown constants of time T, and T 2 agree with the help of logic block 12). The difference Y2 (t) - Y (OD or inverted with respect to the signal Yj (t) or not inverted.

Block 12 logic works as follows.

The phase characteristics of the transfer functions W (P) and Wg (P) may differ from one another in the whole frequency range (i.e., at any frequency of the fundamental harmonic) not more. This means that

tf more than at the end of the transient processes associated with switching on the device, the output of the adder 30 appears pulses, the alternation of polarity of which can have two options. In the first case, time intervals appear with simultaneous switching on of counting triggers 31 and 32, which leads to actuation through And 33 of the actuator 34, which switches switches 8 and 9. The first of them turns off the inverter.

The 10 differences of signals fjn / tO-Y (t) l, which at this impedance is converted into the difference XY (Ј) -Y2 (t) J and the transfer function Wa (.P.) Accordingly becomes equal to

w, p (

eiiverg (1 + tour). (1 + t4-p)

Switch 9 turns on the inverter

11 and thereby adjusts the device to the new expression for the transfer function Wa (P),

those.

with WjjfHee () T (P). In the second case, the executive body does not work, and the device remains in the initial state.

At the second stage, the time constant of the second sensor T is determined. To do this, using block 6, the first model and sensors are adjusted by establishing the synchronicity of the compared signals Y (t) and ЈYt (t) –Y, (t) . From a comparison of the transfer functions of W5 (P) and Wg (P), it follows that the phase shift between the indicated signals can be eliminated by adjusting the gain of the adjustable amplifier, 17 to

one

equal to -,

X2

At this stage, the device operates as follows.

The transmission coefficient of the second model of sensors K is fixed and non-zero, for example,

one

equal to one. With

v k

the correlated signals Yj (t) (t) - Y, (t) will be shifted in time, and depending on the ratio T and T ,, any of these signals may be leading. At the output of the element EXCLUSIVE OR 23, a pair of pulses of the same polarity appear, causing the inclusion of a counting trigger for a time interval equal to the shift between the matched signals. The time interval to voltage converter generates voltages

649308, 6

proportional to shear which

minimized by block 26 for determining the extremum by adjusting the first model 4, tTe. transmission coefficient K, amplifier 17. Minimum of this

voltage is reached at K; - 14

- -. In this case, the pulses at the outputs

T2

10 formers 21 and 22 of different polarity pulses will coincide in time and will not pass through the EXCLUSIVE OR 23 element. The resulting Kq value. is fixed and its inverse

15 at the output of the block 13 for calculating the reciprocal, equal to the constant time T of the second sensor, is recorded by the first recording unit 15.

At the third stage, when determining the time constant T of the first sensor, the obtained gain coefficient of the amplifier 17, 1 is fixed.

20

equal to,

and adjustments are made to

25

Kg Eff. transmitting the second model 5 sensors to a value equal to the difference (-Tg).

The device at this stage works in the following way.

30 The signal at the output of subtraction unit 27 is equal to the difference of the common mode signals, Y3 (t) and Y4 (t) -Y1 (tJ {and its level depends on the degree of difference between the values of K- and the difference (Tf-T2) (see transfer functions W (P) and W6 (P)). The output module of the subtracting unit 27 is minimized by the extremum determination unit 29 by adjusting the transfer rate of the second model K to a value equal to (T ,, -T). the extremum determination unit 29 is equal to 0. The obtained Kg value is summed up 45 (with the corresponding sign) in

adder 14 with the previously found value

By the T. search, the constant T is registered by the second recording unit 16.

This device does not use any constructive parameters of the sensors. For the determination of the constant time, only the input signals of the sensors are used. In the proposed device, there are no simultaneous measurements of several quantities, and the effect of random interference is smoothed using extreme regulators. The device is applicable to sensors of any physical quantities, regardless of their design features.

Claims (4)

1. A device for determining the time constant of physical quantity sensors, containing the first and second sensors with different time constants connected by outputs to the measuring unit of the difference of the output signals of the sensors, characterized in that, in order to improve the accuracy, the first connected and the second model of one of the sensors, the first model being connected to the output of the first sensor, the tuning unit of the first model, the calculating unit of the reciprocal, and the first recording unit, in series first switch connected to the output of the measuring unit of the difference of the output signals of the sensors, the first inverter, the second model setting unit, the second switch, the second inverter, the adder and the second recording unit, the logic unit connected to the second and third outputs, respectively the tuning unit of the first model, and the output to the control input of the first switch, the second input of which is connected to the output of the first inverter and connected to the second input of the tuning unit of the first model, the first the input of which is connected to the second input of the second model setting unit, and the output to the second input of the first sensor model, the second input of the second sensor model is connected and the input of the second switch, the control input of which is connected to the output of the logic unit, and the second output is connected to the input of the adder, the second output connected to the output of the box to calculate the reciprocal. 2. The device according to claim 1, characterized by the heme, that the first model setting unit contains the first null-organ sequentially connected, the input connected to the first input of the first model setting unit, the first driver of the open-loop impulses, the logical element 0 EXCLUSIVE OR, counting trigger,  a time interval to voltage converter and an extremum determination unit connected by an output with an output of a first model tuner, a second input 5 of which, through a series-connected second null-organ and a second driver of different-polarity pulses, is connected to the second input of the logical element EXCLUSIVE OR, the first and 0 whose second inputs are connected to the second and third outputs of the tuner of the first model. 3. Device but nn. 1 and 2, about t-. that block 5, the settings of the second model comprise, in series, a subtracting unit, the first and second inputs connected to the corresponding inputs of the setting unit of the second model, the unit 0 definitions of the module and an extremum determination unit, connected by the output. To the output of the second model tuner. I 4. The device according to PP. 1-3, about t - l and in that the logic block contains a series-connected adder, inputs connected to the corresponding inputs of the logic block, a counting trigger with positive polarity control, a logic element And an actuator, output connected to the output of the logic block, a counting trigger with negative polarity control, connected between the output of the adder and the second input of the logic element I.