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-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
(2) Executing cold junction temperatuer compensation externally (set to
4
- 15 4.7 Cold Junction Temperature Compensation with/without Setting
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-H01
Terminal block
RTD
"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-H01
Terminal block
Compensation conductor
Compensation conductor
Conductor
Ice bath
Object whose temperature
is to be measured
Thermocouple
Object whose temperature
is to be measured
Thermocouple