Honeywell SMV 3000 user manual Cold Junction Compensation Background Output Linearization

6.8 TempConf Configuration - PV3, Continued

Cold Junction

Compensation

Background

Output Linearization

If a thermocouple is used for process temperature PV3 input, you must select if the cold junction (CJ) compensation will be supplied internally by the transmitter or externally from a user-supplied isothermal block.

Specify source of cold junction temperature compensation.

•Internal

•External - Must also key in value of cold junction temperature for reference.

Every thermocouple requires a hot junction and a cold junction for operation. The hot junction is located at the point of process measurement and the cold junction is located in the transmitter (internal) or at an external location selected by the user. The transmitter bases its range measurement on the difference of the two junctions. The internal or external temperature sensitive resistor compensates for changes in ambient temperature that would otherwise have the same effect as a change in process temperature.

If you configure CJ source as external, you must tell the transmitter what cold junction temperature to reference by typing in the temperature as a configuration value. For internal cold junction configuration, the transmitter measures the cold junction temperature internally.

For process temperature (PV3) input, configure output to represent one of these characterization selections.

•	Lineard -	Output is in percent of temperature span.
•	Unlinearized -	Output is in percent of resistance span for
		RTD or millivolts or volts span for T/C.

	d Factory setting.
Background		You can have the transmitter provide a linear output which is linearized to
		temperature for PV3 input, or a nonlinear output which is proportional to
		resistance for an RTD input, or millivolt or volt input for T/C input. Also,
		if you do switch from linear to unlinearized or vice versa, be sure you
		verify the LRV and URV settings after you enter the configuration data.
		Continued on next page

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