9.1.3 To Check Thermocouple Input Calibration

 

Connect a millivolt source, traceable to national standards, to terminals V+ and V- as shown in the diagram below. The mV source must be capable of simulating the thermocouple cold junction temperature. It must be connected to the instrument using the correct type of thermocouple compensating cable for the thermocouple in use.

 

 

Set the mV source to the same thermocouple type as that configured in the controller.

 

Adjust the mV source for minimum range. For a type J thermocouple, for example, the minimum range is -210^OC. However, if it has been restricted using the Range Low parameter then set the mV source to this limit. Check that the reading on the display is within ±0.25% of reading ±1LSD.

 

Adjust the mV source for to the maximum range. For a type J thermocouple, for example, the minimum range is 1200^OC. However, if it has been restricted using the Range High parameter then set the mV source to this limit. Check that the reading on the display is within ±0.25% of reading ±1LSD.

 

Intermediate points may be similarly checked if required.