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Reference
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Cold Junction Compensation.
The ADMUX card has on board cold junction compensation
circuitry. When the two jumper links are connected the Cold
Junction Circuit is connected to Relay 0 on the ADMUX board.
When the two jumper links are removed then Relay 0 is free for
use as a normal input. Do not wire any other inputs to Relay 0
on those boards where the CJC circuitry has been activated. The
jumpers connect Relay 0 input to the cold junction circuit and
Relay 0 return line to ANALOG ground.
The Cold Junction Compensation jumpers are located on the
middle left hand side of the ADMUX board and are labelled
CJC TO REL00 ENABLE.
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Figure 1-8. Activating Cold Junction Compensation.
Using The Cold Junction.
The cold junction, like thermocouples, is usually used in
Differential Input mode. The cold junction circuitry is connected
by jumpers W1 and W2 to the Analog Input Channel 0 and
Channel 0 Return lines. R26, need not be inserted when the CJC
circuitry is in use. When jumpers are not placed across the W1
and W2 shorting headers the cold junction compensation
circuitry does not effect the analog terminal board or the
AD1200 card at all.
The CJC circuitry produces 0.5mVolts per degree Centigrade,
thus by performing an A/D conversion on channel 0 the
temperature of the thermocouples cold junction is known and the
apparent temperature measured by the thermocouple can be
adjusted so that the true temperature of the thermocouple is
known.
Page 8
CJC Circuit Unused. Relay 0 free for normal use.
FACTORY DEFAULT.
CJC Circuit Activated On Relay 0.
Analog Relay Mux Board
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