Transmille EA001A - Manual (Page 14)

EA001A THERMOCOUPLE SIMULATION & MEASUREMENT ADAPTER
OPERATION MANUAL
Transmille Ltd. Page 14
Cold Junction Compensation
Overview
THE EA001A adapter measures the CJC temperature as close as possible to the sensor
in the UUT. Using a high accuracy resistance temperature sensor mounted inside the
EA001A copper plug, the measured temperature is used by the firmware in the calibrator
to calculate the millivolt output required. This method allows any type of thermocouple to
be calibrated without the need for compensation cables, and also reduces the number of
connections, with only high-level signal connections to the calibrator. Transmille have
adopted this method for 3 major advantages.
1: There is no need for a compensation cable for each type of thermocouple to be
simulated. This greatly reduces the number of additional compensating leads required
and reducing errors introduced by using compensation cable.
2: There is only the need for one thermocouple plug working at low levels to connect to
the UUT - other connections to the calibrator are at high signal levels and are
unaffected by thermal emf.
3: The calibrator uses high signal levels and divides the signal down to uV levels in the
EA001A external unit. This results in a quieter, more thermally and emf stable output
and eliminates any self heating effects from the calibrator.