Wiring Checks; Interconnecting Wiring Problem; Thermocouple Checks; Shorted/Failed Thermocouple - Ametek Thermox Series 2000 WDG-IV User Manual

Wiring Checks

Interconnecting Wiring Problem

Thermocouple Checks

Shorted/Failed Thermocouple

Reversed Thermocouple Wires

Thermocouple Compensation

Circuit Check

6-6 | Thermox Series 2000 WDG-IV / IVC / IVCM
Make sure all wiring connections between the control unit
and the sensor are terminated to the proper locations and
are seated properly. This includes ensuring that sets of
wires are not reversed, and that the cable is not damaged
or melted.
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 thermo-
couple.
Check that the thermocouple leads are not shorted to
chassis ground by using an Ohm meter to measure be-
tween 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 thermocou-
ple 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 interconnecting 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 thermocou-
ple). If the thermocouple reads inaccurately, replace it.
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 (-).
using a volt meter, measure across terminals 2 (-) and 12
(+) on the sensor board. If approximately 15 volts is not
present, check that interconnecting wiring is correct. If in-
terconnecting wiring is correct, check across 15V Sup and
15V Com on the control unit for approximately 15 volts. If
15 volts is not present, check fuse F1 on the wiring card.
If this fuse is OK, replace the control unit power supply/
keypad module. If this fuse is not OK, replace the fuse (1/4
amp, 125 volts, IEC speed type FF). Check the intercon-
necting wiring for short circuits before applying power to
the control unit.