Remarks

• If you omit the optional <ch_list> parameter, the configuration applies to the internal DMM, independent of any channels or a scan list (any existing scan list is not redefined). An error is generated if the internal DMM is not installed or is disabled.

• The accuracy of the measurement is highly dependent upon the thermocouple connections and the type of reference junction used. Use a fixed temperature reference for the highest accuracy measurements (you must maintain the known junction temperature). The internal isothermal block reference (34921A only) requires no external wiring but provides lower accuracy measurements than a fixed reference.

• If you select an external reference, the instrument makes thermocouple measurements relative to a previously-stored RTD or thermistor measurement stored in the reference register (see [SENSe:]TEMPerature:TRANsducer:TCouple:RJUNction:EXTernal? command). To store a reference temperature, first configure a multiplexer channel for an RTD or thermistor measurement (see CONFigure:TEMPerature command). Then assign the measurement from that channel as the external reference using one of the following commands:
  [SENSe:]TEMPerature:TRANsducer:FRTD:REFerence
  [SENSe:]TEMPerature:TRANsducer:RTD:REFerence
  [SENSe:]TEMPerature:TRANsducer:THERmistor:REFerence
  
  When you initiate a measurement on an external reference channel (see INITiate or READ? command), the acquired temperature is stored in volatile memory in the reference register. Subsequent thermocouple measurements use the stored temperature as their reference. The temperature remains in memory until you measure a subsequent external reference value in the reference register or remove the mainframe power.

• If you select a fixed reference junction source, you can specify a value between -20 °C and +80 °C using the [SENSe:]TEMPerature:TRANsducer:TCouple:RJUNction command. You must always specify the temperature in degrees Celsius regardless of the temperature units currently selected (see UNIT:TEMPerature command).

• The internal reference junction source is valid only on channels 1 through 40 on the 34921A with the 34921T terminal block installed. An error is generated if you select the internal source on any other module. You can read the internal reference junction temperature using the [SENSe:]TEMPerature:RJUNction[:INTernal]  command.

• The instrument selects the fixed source after a Factory Reset (*RST command). An Instrument Preset (SYSTem:PRESet command) or Card Reset (SYSTem:CPON command) does not change the setting.

Return Format

The query command returns "EXT", "FIX", or "INT" (34921A only) for each channel specified. Multiple responses are separated by commas.

Examples

Example 1:  Selecting a Fixed Reference Junction Source

The following commands select the fixed reference junction source and set the junction temperature to 20 °C on channels 2 and 11 in slot 5.

TEMP:TRAN:TC:RJUN:TYPE FIX, (@5002,5011)
TEMP:TRAN:TC:RJUN 20, (@5002,5011)

Example 2:  Selecting an Externally-Referenced Source

The following commands configure multiplexer channel 3 in slot 1 for thermocouple measurements and select an external reference junction for that channel.  

CONF:TEMP TC,J,(@1003)
TEMP:TRAN:TC:RJUN:TYPE EXT,(@1003)

The following commands configure multiplexer channel 1 in slot 1 for thermistor measurements and assign this channel as the reference channel.

CONF:TEMP THER,5000,(@1001)
TEMP:TRAN:THER:REF ON,(@1001)

The following command sets up a scan list that contains both the reference channel (channel 1) and the thermocouple channel (channel 3). If you do not include the reference channel in the active scan list, the instrument uses the temperature previously stored in the reference register. The INITiate command initiates the scan.

ROUT:SCAN (@1001:1005)
INIT

Example 3:  Querying the Reference Source

The following query reads the reference junction source on channels 2 and 11 in slot 5.

TEMP:TRAN:TC:RJUN:TYPE? (@5002,5011)

Typical Response:  FIX,FIX

See Also

CONFigure:TEMPerature

[SENSe:]TEMPerature:RJUNction[:INTernal]

[SENSe:]TEMPerature:TRANsducer:FRTD:REFerence

[SENSe:]TEMPerature:TRANsducer:RTD:REFerence

[SENSe:]TEMPerature:TRANsducer:TCouple:RJUNction

[SENSe:]TEMPerature:TRANsducer:TCouple:RJUNction:EXTernal?

[SENSe:]TEMPerature:TRANsducer:THERmistor:REFerence

UNIT:TEMPerature