Ratio Error
Example
This example demonstrates how to compute the total measurement error
when using the Ratio Function. Assume a ratio measurement is made
with the following conditions:
• Channel 1, 5 V input on the 10 Volt range
• Channel 2, 10 mV input on the 10 mV range
To compute the total measurement error using the 90-day accuracy
specifications:
Ratio Error % = Channel 1 accuracy in % + Channel 2 accuracy in %
Channel 1 Reading Error % =
0.0020%
Channel 1 Range Error % =
0.0004% ∗
Range
Reading
= .0004% ∗
10
5
= .0008%
Total Channel 1 Error % = 0.0020% + 0.0008%= .0028%
Channel 2 Reading Error % =
0.0040%
Channel 2 Range Error % =
0.0002% ∗
Range
Reading
= .0002% ∗
10 mV
10 mV
= .0002%
Total Channel 2 Error % =
0.0040% + 0.0002%= .0042%
Ratio Error % = 0.0028%
+ 0.0042% = .0070%
Ratio =
5 V
10 mV
= 500 ± 0.0070% = 500 ± 0.035
For Ratio Measurements, if both input channels use the same range, use
0 for the % of reading error.
Chapter 8
To Calculate Total Measurement Error
284
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