4
Product Specifications
46
Agilent U2802A 31-Channel Thermocouple Input User’s Guide
Calculating System Accuracy
The overall measurement system comprises of three major components:
1
DAQ (U2355A or U2356A)
2
Signal Conditioner (U2802A), which includes CJ Sensor error
3
Sensor (Thermocouples)
Errors introduced by each of the above components has to be accounted
for when calculating the total system accuracy. Since errors from each
component are not correlated with each other, the total system error will
be the root- sum- square (RSS) of all the errors:
E
TOTAL
2
= E
DAQ
2
+ E
SIG_COND
2
+ E
THERMOCOUPLE
2
Example:
Assume the following conditions:
•
DAQ: Agilent U2355A
•
Signal Conditioning: Agilent U2802A
•
Ambient temperature: 23 °C
•
Thermocouple type: J- type, standard limits of error
•
Temperature to measure: 600 °C
Assume the following error specifications:
•
U2355A: Gain error = 0.02% of reading
•
Offset error = 1 mV
•
U2802A gain = 97.673
•
Gain error = 0.06% of reading
•
Offset error = 15 µV (with respect to input)
•
Zeroing error = 6 µV (with respect to input)
•
CJ measurement accuracy = 1 °C
•
Thermocouple = greater than 2.2 °C or 0.75% error
•
Noise error has been omitted to simplify the example
U2802A_UG.book Page 46 Friday, November 25, 2011 10:57 AM
