Specifications

Analog Input Modules
168
31007715 6/2008
The following example illustrates the key points reported to the status register
temperature for an IEC Platinum Pt1000 RTD sensor. The temperature input data is
shown in degrees C along the y-axis and in decimal format along the x-axis:
Cold-junction
Compensation
Register
Cold-junction compensation provides improved temperature measurement in TC
mode. The STB ART 0200 sends the cold-junction compensation temperature value
to the NIM and the fieldbus as the fifth register in the STB ART 0200 process image
block. The data has15-bit + sign resolution.
The register represents temperature data as degree C x 10 or degrees F x 10. For
example, if the compensation temperature is 74.9 degrees C, the register
representing that channel reads 748 (in decimal) or 0x1F2 (in hexadecimal). You
can configure degrees C or degrees F in the module editor (see p. 160).
Cold-junction compensation can be effected by either internal or external
compensation (see p. 163). The module has two internal sensors that can be used
for internal cold-junction compensation. The two sensors calculate the
compensation for each channel, and the module reports the average of the two
sensed temperatures as compensation data to the process image.
External cold-junction compensation requires that you connect an external RTD
device to the top connector on the module. The module uses the real temperature
of the RTD for external cold-junction compensation. It reports the real temperature
as compensation data to the process image.
Temperature in °C
8500
8296
850 °C
829.6 °C
-195.2 °C
-200°C
-2000
-1952
Decimal
ORE
ORW
URE
URW
display
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