Early Burnout Detection (only for MTL4075, MTLx573, MTLx575 and MTLx576)

This feature is an aid to anticipate the failure of thermocouple sensors.  With age and exposure to temperature cycling the junction of the two dissimilar thermocouple materials starts to break down and eventually becomes an open circuit.  This is commonly known as “burnout” of the sensor.  Most temperature converters provide the option to drive the output signal upscale or downscale when the sensor becomes open-circuit to activate process protection or to warn the operators (open circuit alarm).

Early Burnout Detection (EBD) enables the monitoring of the sensor connection to detect increasing loop resistance which can forewarn of the sensor breakdown.

When the converter is powered up, or after re-connection of a thermocouple sensor, the loop resistance is measured and stored as a reference.  If the loop resistance increases by more than 50ohms then the EBD alarm is activated (relay on and LED lit).  Note that this does not initiate upscale or downscale drive activity until the input connection is detected to be an open circuit.

The alarm condition is reset and a new base value of loop resistance is stored after the input thermocouple circuit is open-circuited (remove the connector) or the power is interrupted.