SU1560988A1 - Device for measuring temperature - Google Patents

Abstract

The invention relates to the field of temperature measurements and can be used to control the temperature of the heat insulating surface of boiler equipment and heat pipes in thermal power plants. The aim of the invention is to simplify the construction while maintaining the independence of the measurement accuracy on the magnitude of the supply voltage. The voltage of the source 5 through the converter 2 voltage - the current flows to the thermal converter 1 resistance, the free output of which is grounded. The voltage of the thermocouver 1 is supplied to one of the inputs of the comparison unit 8. The second input of the unit 8 is connected to the capacitor 4, one output of which is grounded, and the second through the switch 3 is connected to the source 5, the output of the controlled generator 7 and the second input of the comparator unit 8. Initially, the switch 3 is closed and the capacitor 4 is charged power supply U _p source 5. The signals of the control unit 6, the key 3 is opened, and the capacitor 4 receives its quantizing pulses from the controlled generator 7. When the voltage on the capacitor 4 and the thermal converter 1 are compared, the signal from the output of the unit 8 compare stops the controlled generator Ator 7. The number of pulses accumulated by the controlled generator 7 is recorded by a digital counter 9 with an indication proportional to the measured temperature and does not depend on the value of the supply voltage. 1 il.

Description

The invention relates to a technique of temperature measurements and can be used in thermal electric power stations to control the temperature of the surface of heat insulation of boiler and turbine equipment and heat pipes.

The purpose of the invention is to simplify the design while maintaining the independence

 bridges of measurement accuracy on the magnitude of the supply voltage.

The drawing shows a functional diagram of the proposed device.

The device contains a resistance thermocouple 1, a voltage converter 2 — current, a switch 3, a capacitor 4, a supply voltage source 5, a control unit 6, a controlled quantizing pulse generator 7, a comparison unit 8, and a digital counter 9 with an indication.

The device works as follows

The voltage of the source 5 of the supply voltage is converted by the converter 2 a voltage — a current into a current, JQ supplied to a resistance thermocouple 1, on which a voltage drop UR I RT is created, where R is the resistance of the thermal converter 1; I - current in the circuit of the thermocouple transducer 75, provided by the converter 2 voltage - current.

This voltage is applied to the first input of the comparison unit 8. Initially, capacitor 4 is connected to source 20 via a closed switch 3, as a result of which capacitor 4 is charged to a voltage Un.

According to the signal from the control unit 6, the key 3 disconnects the source 5 of the supply voltage from the capacitor 4. At the same time, another signal from the control unit 6 starts the generator 7 of quantizing pulses.

Under the influence of the pulses of the generator 7, the capacitor 4 changes its charge. When the voltage across the capacitor 4 reaches the value U R, the comparison unit 8 starts and the generator of the pulses 7 stops. The number of pulses accumulated by generator 7 of pulses, recorded by counter 9 with indication, is proportional to the value (Un-Ug) depending on resistance RT, and therefore on 4Q temperature. Then, at time determined by control unit 6, switch 7 again closes connects the capacitor 4 to the source 5 of the reference voltage and the measurement cycle repeats.

In this case, the dependence of the number of pulses N of the generator 7 pulses on the value of the resistance of the thermal converter and the corresponding heme-. Perurature will be defined by the expression:

35

H- U

N di

(one)

where dU is the quantum of voltage variation on the capacitor 4 under the influence of a single impulse from the generator 7.

Current I in the converter circuit 2 voltage - current is determined by the value of the supply voltage Uп

1 and and „,

where p is the conversion factor

Converter 2. With this in mind, expression (1) can be represented as:

 Ml-J / Rr) UA ju (J / A / -Kg)

whether

 Uff KRo-Rr)

whether

dU

(2)

0

five

0 Q

.

five

five

where Re is the resistance of the thermal converter 1, in which the voltage drop across the thermal converter is equal to the voltage on the capacitor 4. When the magnitude of the supply voltage Un changes, the amplitude of the pulses of the quantizing oscillator 7 changes proportionally, which causes a corresponding change in dU. As follows from (2), the value of the indications of the device remains unchanged.

Claims (1)

Invention Formula A temperature measuring device comprising a power supply source, a resistance thermocouple, a key whose control input is connected to the control unit, and a series-connected quantizing pulse generator and a digital counter with an indication that is simple to maintain accuracy of measurement from the magnitude of the supply voltage; a voltage converter — a current, a comparison unit, and a capacitor — are introduced, and the quantizing electric generator is controllable with input voltage; Starting and stopping waters connected respectively to the control unit and to the output of the comparison unit, the supply voltage source being connected to the resistance thermocouple via a voltage to current converter} the free output of the resistance thermocouple is grounded, the key input is connected the key output is connected to the output of a controlled quantizing pulse generator and to a capacitor, the free output of which is grounded, as well as to one of 15609886 the inputs of the comparison unit, the 4th input of which is connected with the output of the voltage converter — current.