Chapter 4 Features and Functions

Temperature Measurement Configuration

Thermocouple Measurements

To connect a thermocouple to the module’s screw terminals, see page 21.

∙The instrument supports the following thermocouple types: B, E, J, K, N, R, S, and T using ITS-90 software conversions. The default is a J-Type thermocouple.

∙Thermocouple measurements require a reference junction temperature. For the reference junction temperature, you can use an internal measurement on the module, an external thermistor or RTD measurement, or a known fixed junction temperature.

∙If you select an external reference, the instrument automatically reserves channel 01 on the multiplexer in the lowest slot as the

 

reference channel (thermistor or RTD measurement). If you have

 

 

more than one multiplexer installed, channel 01 on the module in the

 

 

lowest slot is used as the reference for the entire instrument.

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∙

Before configuring a thermocouple channel with an external

 

 

reference, you must configure the reference channel (channel 01)

 

 

for a thermistor or RTD measurement. An error is generated if you

 

 

attempt to select the external reference source before configuring the

 

 

reference channel. An error is also generated if you change the

 

 

function on the reference channel after selecting the external

 

 

reference for a thermocouple channel.

 

∙ If you select a fixed reference temperature, specify a value between -20 °C and +80 °C (always specify the temperature in °C regardless of the temperature units currently selected).

∙ 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. The internal isothermal block reference provides the lowest accuracy measurements. For more information on reference junction temperature measurements and associated errors, see the discussion starting on page 352.

∙ The thermocouple check feature allows you to verify that your thermocouples are properly connected to the screw terminals for measurements. If you enable this feature, the instrument measures the channel resistance after each thermocouple measurement to ensure a proper connection. If an open connection is detected (greater than 5 kΩ on the 10 kΩ range), the instrument reports an overload condition for that channel (or displays “OPEN T/C” on the front panel).

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