SU1287041A1 - Method of telemetering increment of resistance of resistive transducer by means of two-wire circuit - Google Patents

Abstract

The invention relates to the measurement of the increment of active resistance and the values converted into an increment of active resistance, for example, the temperature of sensors remotely located from the recording equipment and connected to it by means of a two-wire communication line. working in conditions of variable and high temperatures. The purpose of the invention is to improve the measurement accuracy of the resistance increment of a resistive sensor in severe conditions of operating the communication lines - achieved by eliminating the influence of the communication line parameters on the measurement result. The device implementing the method comprises a resistive sensor 1, an exemplary resistor 2, reference elements 3 and 4, a two-wire communication line 5, a current generator 6, a voltage converter 7 - a code and a microprocessor 8., The voltage at the output of the communication line 5 in Each measurement cycle is converted in the converter 7 into codes that enter the microprocessor 8. In this microprocessor, the resistance increment of the resistive sensor is determined by the algorithm described in the description of the invention. 3 il. (L

Description

/, -I I,. . ±

one

, . ±

}

FIG. 2

The invention relates to measuring the increment of the active resistance and the quantities converted into the increment of the active resistance, for example temperature, sensors remotely located from the recording equipment and connected to it using a two-wire communication line operating under conditions of variable and high temperatures.

The aim of the invention is to improve the measurement accuracy of the resistance increment of a resistive sensor. 3 difficult operating conditions of the communication line by eliminating the influence of the communication line parameters on the measurement result.

Fig. 1 is a diagram illustrating the proposed measurement method in Fig. 2, a block diagram of a device implementing the proposed method; FIG. 3 shows the characteristics of the support — Hbfx elements included in the sensor.

The device contains a resistive sensor 1, an exemplary resistor 2, the first and second supporting elements 3 and 4, a two-wire communication line 5, a current generator 6, a voltage converter 7 — a code, and a microprocessor 8.

The method for measuring the resistance increment of a resistive sensor is as follows.

In the first cycle, the voltage at the output of the communication line 5, loaded on the first exemplary voltage and the resistive sensor 1, created by the current jump I and determined by the ratio

.- vi: l |; t j- ,. (ABOUT

where are the resistances of the communication circuit equivalent circuit resistors (Fig. 1);

-

R.

E

- resistance of the resistance sensor;

is the value of the first reference voltage of the support element 3.

In the second measurement cycle, the communication line 5 is loaded onto the second reference voltage and the reference resistor 2. At the output of the communication line 5, a voltage appears

P-tGt + 5l l5 l + F5i- -HT

g × R, .R, + RO, + R, RO

where RQ is the resistance of the reference resistor 2;

E- is the value of the second reference voltage of the support element A.

In the third and fourth cycles, similar measurements are made of the voltage at the output of the communication line 5 created by a current of a different amplitude, and the ratio of the amplitudes is equal to the coefficient K. These voltages are written as

, Pv R3 + Rx) l. R-,

 R + RJ + RX

R) 1

 R, + R, + RO J

+ E,

+ E

R, j + R, + R /

 RI

2R + Rj + R

(3)

(four)

Together solving the equations (1) - (4), we obtain the final ratio

lr - ed.e (k-1) si. + i) f.

x 1 (ki, s) (ki, s)

where & R is the increment of resistance

resistive sensor; I - the amplitude of the current in the first 2

measurement cycles; K - coefficient equal to the ratio of the current in the second 2 measurement cycles to the current in the first 2 cycles; Е ,, Е2 - values of the first and second

model voltages; and, and, and 1) 4 is the voltage at the output of the communication line corresponding to the first, second, third, and fourth measurement cycles.

A device that implements the proposed method works as follows.

In the first, second, third and fourth measurement cycles at the output of the current generator 6, the currents I, -I, KI and -KI are set, respectively. The voltages at the output of communication line 5 in each measurement cycle are converted — in converter 7, voltage — code into codes that enter microprocessor 8, microprocessor 8 determines the resistance increment of a resistive sensor according to algorithm (6).

Claims (1)

Invention Formula A method for remotely measuring the resistance increment of a resistive sensor using a two-wire circuit, in which a positive amplitude of current jump is applied to the input of a communication line with the sensor, and the voltage at the input of the communication line is measured, then, a negative amplitude of the current surges is fed to the input of the communication line with the reference resistor connected to it, and the voltage is measured, in order to increase the accuracy change the amplitude of the current jump and reapply the positive amplitude of the current jump, measure the voltage at the input of the communication line, and then apply the negative amplitude of the current jump and measure the voltage, and the increment value is determined by the formula .t -EiEz (K: l) (yj, -y, 3Ui ± Ui).   I (KU, -U4) (KU, -UO E,, E2 ,, and ,, and, and incremental resistance of the resistive sensor; - current amplitude in the first two measurement operations; - a coefficient equal to the ratio of the current amplitude in the second two measurement operations to the current amplitude in the first two operations; -the value of the first and second exemplars; U4 is the voltage at the output of the communication line corresponding to the first, second, third, and fourth measurement operations. E, and fpuej and Fi.Z