6. Series 8 I/O
Configuration
6.7. Defining Analog Input Channel Blocks
186
Series 8 I/O User's Guide
R500
Honeywell
April 2017
Determining Thermal Conversion
Thermal linearization is performed on thermocouple and RTD input types. All
thermocouples (#therm) listed in the
PVCHAR
parameter definition, are supported by
the analog input point. The range of the thermocouple type used with the TC/RTD
channel can be increased by selecting Extended as the entry for the
TCRNGOPT
parameter.
The TC/RTD channels calculate the reference junction compensation from the measured
reference junction output level. This value is stored and then later converted back to
microvolts, with respect to 0 degrees C, for each thermocouple that is to be compensated.
The cold-junction reference compensation (PVREFJN) parameter is expressed in
microvolts for the specified thermocouple and is added to the microvolt value for
PVRAW.
All RTDs (*RTD) listed in the PVCHAR parameter definition, are supported by the
analog input point:
For an RTD, the TC/RTD channels calculate the lead-wire compensation and then
subtract the value from PVRAW. The maximum allowable lead-wire resistance and
intrinsic safety barrier resistance for the RTDs are listed in the table below.
Table 51 RTD lead wire characteristics