Question

Explain the cold tip compensation in thermocouples. Find any data collection hardware / card that offers a solution to this problem and a sign conditioner compatible with this card and write the brand / model and solution in detail. Choose equipment that can be connected to several different types of thermocouples. Please be legible. Thanks.

Answer 1

The thermocouple generates a difference potential proportional, but not linear between the short circuit in the tip and the conductor, cold tip is a reference to the lower temperature of the junction of the thermocouple with the electronics circuit respect to the tip.

To compensate the temperature difference and improve readings, it's necesary to measure the temperature of the conductors of the thermocuple and add dc values accordingly, a simple solution is compensating the ambient temperature with the device is the LM35, a temperature sensor that generates10mV per degree centigrade in the circuit, by implementing a summing OPAMP with the signal from the thermocouple, and choosing an adequate gain, the output is compensated from the cold tip.

Any type of thermocouple can be used by adjusting potentiometer R3.

Another solution is LTC2983, a more accurate integrated solution for thermocouples (type B, E, J, K, N, S, R, T).