Ametek CEM/Humox, Руководство пользователя

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Maintenance and Troubleshooting
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6-9
Thermocouple Checks
Open thermocouple
Remove power to the control unit and the sensor. Measure across terminals “C”
and “D” on the sensor board with an ohm meter. If an open is measured, replace
the thermocouple.
Shorted/Failed thermocouple
Check that the thermocouple leads are not shorted to chassis ground. To do this,
use an ohm meter to measure between terminal C on the sensor board and chassis
ground, and between terminal D on the sensor board and chassis ground. If shorted,
replace the thermocouple.
To verify that the interconnecting cable for the thermocouple is not shorted together,
remove the thermocouple wires from terminals C and D on the sensor board and
measure across terminals 5 and 6 on the sensor board. If shorted, correct the inter-
connecting problem.
To verify the operation of the thermocouple itself, remove the thermocouple from
the sensor and heat its ceramic tip to a known temperature. Measure the millivolt
output with a proper temperature indicating meter (Type K thermocouple). If the
thermocouple reads inaccurately, replace it.
Reversed thermocouple wires
First, have one of the control unit display lines show the sensor cell temperature. If
the thermocouple leads are reversed, the displayed temperature will be decreasing
as the sensor warms up (this will usually happen at start-up or after you replace
a thermocouple). This indicates that the thermocouple wiring is reversed. If you
just replaced a thermocouple, check the leads from the thermocouple to the sensor
board - yellow wire connects to terminal C (+), red wire connects to terminal D (-).