How to measure the average temperature in thermocouple image?

1. How to average temperature is measured with a thermocouple

is shown in the following circuit, insert calibration resistor, R = covenant. 500Ω , according to the thermocouple and compensate the length of the cable connection circuit in the side. In fact, in many cases it is placed in the J. In the BOX.

for three or more, also can use the same measurement circuit.

2。 The average temperature measurement error

( 1) To change the average temperature measurement circuit is shown below.

R1, r2 line resistance, including thermocouple and

R1, r2 'compensation cable: insert resistance

E1 and E2: thermocouple thermoelectric emfs

( 2) Circuit calculation

of circuit of image when using the above formula calculation error,

so, because when meet the R1 = R2, error goes to zero,

R1 = R1 + R1, R2 = R2 + R2 '

using this relationship, as for R1 - R2 insert R1 and r2 'big enough, the line resistance, can reduce the error of the average temperature measurement circuit. Moreover, due to allow the line resistance according to the type of the receiver is restricted, inserting resistance must be determined within the scope of the permit.