Rtd Error; Thermocouple Error - Allen-Bradley 1756-IF8I User Manual

RTD Error

Module error on the 1756-IRT8I or 1756-IR12 module that is used with an
RTD input is defined in ohms. The error is calculated across the entire input
range selected, not the available range of a sensor used with the module. For
example, if the 1...500
510 Ω (actual range = 0...510
The error in ohms translates to temperature, but that translation varies because
the relationship is non-linear. The most effective way to check the module error is
to calculate the error in ohms and use that value in a linearization table to check
the temperature error.
If the module is calibrated at operating temperature and the operating
temperature remains relatively stable, calibration accuracy is better than 0.05% of
the full range. This 0.05% value is a worst case value. In other words, with the
1...500 Ω input range that is selected, the worst case module error is 0.255
Finally, you must check an RTD linearization table to determine how the
temperature error of 0.255
For example, if the module has a 0.05% (or 0.255
of 0 °C (32 °F), the temperature error is ±0.65 °C (±1.17 °F) when the Platinum
385 sensor type is used. This same error at a temperature of 200 °C (392 °F)
translates to a temperature error of ±0.69 °C (±1.26 °F).

Thermocouple Error

Thermocouple error on the 1756-IRT8I or 1756-IT16 at 25 °C (77 °F) indicates
the module's accuracy in measuring temperature. This accuracy varies depending
on these factors:
• Input range = -100...100 mV.
• Thermocouple sensor type, any of the following:
– Type B
– Type C
– Type D
– Type E
– Type J (1756-IT16 default value)
– Type K (1756-IRT8I default value)
– Type N
– Type R
– Type S
– Type T
– Type TXK/XK (L)
Rockwell Automation Publication 1756-UM540E-EN-P - December 2017
Ω input range is used, the module error is calculated across
Ω ).
Ω translates.
Analog I/O Module Features Chapter 2
Ω
Ω ) error and is at a temperature
.
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