Calibration of RTD type Temperature Transmitter

v  Equipments required

a)      Temperature Transmitter,

b)      24 VDC power supply

c)      Multimeter digital

d)      Decade (Resistance) box.


v  Formula for calibration:

Formula: - Rt = R0+αt

For a pt100 RTD:

α = 0.385

R0 = 100.


v  Procedure of RTD

Temperature transmitter Calibration:

Ø  Remove the temperature element (RTD) from the transmitter.

Ø  Connect the circuit as shown in figure above.

Ø  Put multimeter in ma.

Ø  By the equation we can find what will be the output resistance of RTD in specific temperature.



Example:   Range: - 0° C ~ 200° C

Formula: - Rt = R0+αt

Let‘s take the temp= 50°C

 

R50°C = 100+0.385*50

=100+19.25     =119.25Ω Ans,

Temperature

Resistance

O/P Current

0°C

100 Ω

4ma

50°C

119.25 Ω

8ma

100°C

138.5 Ω

12ma

150°C

157.75 Ω

16ma

200°C

177 Ω

20ma

  • Ø  So by the equation we can find resistance values for 5 point calibration (4ma,8ma,12ma,16ma,20ma)
  • Ø  By setting these resistance values using decade box we can find the corresponding ma in multimeter.
  • Ø  By changing the zero and span potentiometer in transmitter we can do the 5 point calibration.

  1. Ø  Repeat the process.