SU1332163A1 - Device for multipoint measurement of temperature in explosion hazard medium - Google Patents

Abstract

The invention relates to the measurement of temperature using resistance thermocouples. The purpose of the invention is to increase the speed of the device. Through a resistive temperature transducer (TC) a current flows proportional to the voltage at the output of the equalizer 14, and the input of the measuring amplifier (IC) 12 receives the voltage from the TC 1. The voltage from the output of the IC 12 at the adder 13 is compared with the source voltage 19 of the reference voltage and the difference is fed to the input of the offset 14. The voltage on the TC 1 is maintained constant and proportional to the reference voltage, and the current flowing through it flows through the reference resistance 15 and creates a voltage drop across it, the measured Lemma 16, the voltage output from the latter through an analog-digital converter 17 is supplied to the computing unit to the indicator 18, and by its value and the value of the reference voltage determined by the resistance value of TA 1 which is proportional to the measured temperature. 3 il. W from 00 to 1C O5 oo (ya /

Description

one

The invention relates to the measurement of temperature using resistance thermocouples, in particular to the measurement of temperature in an explosion hazardous environment.

The aim of the invention is to improve the speed of the device.

FIG. 1 is a diagram of a device for multipoint temperature measurement in an explosive atmosphere; FIG. Fig. 2 is a block diagram of a voltage control system on a measured resistance thermocouple; in FIG. 3, the electrical circuit of the control object is equivalent.

A device for multipoint temperature measurement in an explosive environment (Fig. 1) contains n measuring channels (the number of channels can be any), each of which includes a resistance thermal converter 1 connected to the rest of the elements by a four-wire communication line with two current 2 and 3 and two potential 4 and 5 wires having a distributed capacitance 6 (capacity 6 in the drawing is conventionally shown by a dashed line), resistances 7.1–7.3 of spark protection and keys 8–10, the control inputs of which are connected to block 11 channels for prison, an additional measurement amplifier 12, an adder 13, an equalizer 14, a reference resistor 15, a measuring amplifier 16j analog-to-digital converter 17, the calculation unit 18 with a digital output and an indicator, a source of reference voltage 19.

The block diagram of the voltage regulation system on the measured resistance thermocouple (Fig. 2) consists of an adder 13, a corrector 14 with a transfer function Wb (P), an adjustment object 20 with a transfer function Wp (P) and a measuring amplifier 12 with a transfer function W, (P).

The corrector 14 may be implemented, for example, in the form of a measuring amplifier with a transfer characteristic and (P) Cc. If a system with such a corrector is unstable, then more complex correctors can be used, for example, in the form of an integrator with the transfer function W ((P)

five

0

five

0

five

0

five

0

five

1632

KK - providing the necessary statistical properties of the control system, given the speed and stability of the system.

The control object (Fig. 3) includes resistance thermocouple 1, capacitance 6 of the communication line wires, resistance 7.1 and 7.2 spark protection, total resistance 21 key 10 and resistance 7.3 spark protection and a reference resistance 15.

The device works as follows.

According to the signal of the channel switching unit 11, the thermal converter 1 of the resistance of the selected channel is connected to the output of the corrector 14 through the reference resistance 5 switch 10, the resistance 7.3 of the spark protection and wires 3 and 2 through the test circuit, as well as to the input of the measuring amplifier 12 through potential wires 4 and 5, resistances 7.1 and 7.2 of spark protection and switches 8 and 9. At the same time, a current proportional to the voltage at the output of the equalizer 14 flows through the resistance thermal converter 1, and a voltage goes to the input of the measuring amplifier 12 Thermal transducer 1 resistance.

The voltage from the output of the measuring amplifier 12 on the adder 13 is compared with the voltage of the source 19 of the reference voltage and their difference is fed to the input of the equalizer 14. Thus, a closed system of automatic voltage regulation on the thermal resistance 1, whose structural diagram is shown in Fig. 2, is formed. , and the basic electrical circuit of the object of regulation in FIG. The voltage on the thermocouple resistance is kept constant and proportional to the reference voltage, and the current flowing through it flows through the reference resistance 15 and creates a voltage drop across it, which is measured by the measuring amplifier 16, i.e. the voltage at the output of the measuring amplifier 16 is proportional to the current flowing through the thermal resistance 1. The voltage from the output of the first measuring amplifier 16 through the analog-to-digital converter 17 enters the computing unit 18 with the indicator and the value of the resistance of the thermal converter is determined by its value and the value of the reference voltage 1 R, which is proportional to the measured temperature.

The transfer function of the closed-loop control system is

W (p) H KlPl iWfiP) (,.

 l-bWK (P) -We (P) -W, (P) The transfer function of the control object (Fig. 3) has the form

"T / TG (2) where Kf -f-V -; - R ;;

t 2 Сл1К2 ± К 1К9.

in Re + R, + RU

RJ is the resistance of the reference resistance 15; R, - resistance resistance

7 spark protection;

C is the capacitance of the wires of the communication line. If the operational amplifiers entering the second measuring amplifier and the equalizer are considered ideal, then the transfer function of the measuring amplifier can be written as

W, (P) KV (3) and the transfer function of the corrector 14

W, (P) KK, (4)

Let K | 1, then the substitution. (2). (3), (4) and (2) gives

W, (P)

Kkk

(TeP-0 (

Kk ke

(KK.iy (

Thats

P + 1)

A comparison of (2) with (5) shows that the choice of the transfer coefficient of the 14 K corrector can make the time constant in the closed control system as small as desired, which means that the speed of the system is as large as desired.

The static accuracy of the control system is determined by the magnitude of the static error, which is equal to

X

Uon

l + Wp (P)

U

p-0

I + K K,

(6)

where UD is the reference voltage of the source 19 of the reference voltage. Thus, by increasing the coefficient Kc, we can achieve the necessary

from 10

20

25

. , thirty

35

40

45

50

55

.

static accuracy of the system and its speed, and hence the necessary static accuracy and speed of the entire device for multipoint temperature measurement in an explosive environment.

Claims (1)

Invention Formula The device dp multipoint temperature measurement in an explosion-hazardous environment, containing n measuring channels, each of which consists of a resistance thermal converter connected to a four-wire communication line, and three keys on field-effect transistors, a switching unit connected to the keys, a reference resistor, the first terminal of which is connected to the outputs of the third switches of all measuring channels, the measuring amplifier, whose input is connected to the first and the second terminals of the reference resistor a, and the output is connected to the input of an analog-digital converter, the output of which is connected to the input of the computing unit with a digital output and an indicator, characterized in that, in order to increase the speed of the device, a corrector, a source of reference voltage, an adder, three channel resistance, spark protection and an additional measuring amplifier, whose inputs are connected, respectively, to the outputs of the first and second keys of all measuring channels, and the output is connected to the first input of the adder, the second input of which o is connected to the output of the reference voltage source, and the output is connected via a corrector to the second output of the reference resistor, with B of each measuring channel the first current output of the resistance thermal converter through the first wire of the communication line to the common bus of the device connection and the third spark protection resistance is connected to the input of the third key, and potential outputs of the thermal converter through the third and fourth wires of the communication line and the first and second terminals resistivity iskrozashchity connected respectively to the inputs of the first and second keys. and. 13 on 75 Editor G. Volkova Compiled by V.Kulikov Tehred M. Khodanich Proofreader I. Muska Order 3823/37 Circulation 776 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5  - - - - --- - -------- - - - ------- --- - “----- - --.-. - .- .. ... .. „ Production and printing company, Uzhgorod, Projecto st., 4 FIG. 2 21 1.2 -0 .-. e Fig.Z