Cold Junction Temperature Compensation With/Without Setting - Mitsubishi Melsec-Q Series User Manual

4
SETUP AND PROCEDURES BEFORE OPERATION
4.7

Cold Junction Temperature Compensation with/without Setting

The Q68TD-G-H02(H01) can execute the following two different cold junction temperature
compensations by setting the inteligent function module switch setting (switch 4) to
whether to carry out the cold junction temperature compensation using the cold junction
temperature compensation resistor (RTD) or not.
(1) Executing cold junction temperature compensation with the cold
junction temperature compensation resistor (RTD) (set to "with cold
junction temperature compensation")
Cold junction temperature compensation is possible by connecting the supplied cold
junction temperature compensation resistor (RTD) and setting it to "with cold junction
temperature compensation".
Always connect the supplied cold junction temperature compensation resistor (RTD)
to the terminal block. (For connection, refer to Section 4.4.2.)
Q68TD-G-H02(H01)
Figure 4.11 Connection between a cold junction compensation resistor (RTD) and a relay terminal block
(2) Executing cold junction temperatuer compensation externally (set to
"without cold junction temperature compensation")
Use this function to measure temperatures at high accuracy when the cold junction
temperature compensation accuracy ( 1 ) of supplied cold junction temperature
compensation resistor (RTD) cannot be taken as a margin of error.
Connecting a cold junction temperature compensation resistor (RTD) to the terminal
block is unnecessary.
By providing a precision ice bath externally, the thermoelectromotive force generated
at the tip of the thermocouple can be led to this module without any change, improving
the cold junction temperature compensation accuracy.
Q68TD-G-H02(H01)
Figure 4.12 Connection between an ice bath and a relay terminal block
Terminal block
RTD
Compensation conductor
Terminal block
Conductor
Ice bath
4.7 Cold Junction Temperature Compensation with/without Setting
Object whose temperature
is to be measured
Thermocouple
Object whose temperature
is to be measured
Compensation conductor Thermocouple
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