Product Specifications
4
Agilent U2802A 31-Channel Thermocouple Input User’s Guide
47
With zeroing, the offset errors from the DAQ and the U2802A can be
removed, and replaced with the zeroing error.
Based on the ITS- 90 Thermocouple table, a J- type thermocouple will
output 33.102 mV at 600 °C, and changes at a rate of approximately
59 µV/°C. This corresponds to (33.102 mV
×
97.673) or 3.2332 V at the
input of the DAQ.
Hence, E
DAQ,
E
SIG_COND,
and E
ZEROING
are calculated as follows:
•
E
DAQ
= 0.02%
×
33.102 mV
= 6.62 µV
= 6.62 µV ÷ 59 µV/°C
= 0.112 °C
•
E
SIG_COND
= (0.06%
×
33.102 mV) ÷ 59 µV/ °C
= 0.337 °C
•
E
ZEROING
= 6 µV ÷ 59 µV/°C
= 0.102 °C
Next, the cold junction sensor error is calculated.
At 23 °C, a J- type thermocouple output voltage changes at a rate of
52 µV/ °C. Thus, the CJ sensor error of 1 °C at 23 °C corresponds to
52uV/ °C
×
1°C = 52 µV.
At 600 °C,
•
E
CJC
= 52 µV ÷ 59 µV/°C
= 0.88 °C
U2802A_UG.book Page 47 Friday, November 25, 2011 10:57 AM
