HP 34970A User Manual page 410

Chapter 9 Specifications
To Calculate Total Measurement Error
Understanding the " % of range " Error The range error compensates
for inaccuracies that result from the function and range you select.
The range error contributes a constant error, expressed as a percent of
range, independent of the input signal level. The following table shows
the range error applied to the DMM 's 24-hour dc voltage specification.
Range Input Level
10 Vdc 10 Vdc
10 Vdc 1 Vdc
10 Vdc 0.1 Vdc
Total Measurement Error To compute the total measurement error,
add the reading error and range error. You can then convert the total
measurement error to a "percent of input" error or a "ppm (part-per-
million) of input" error as shown below.
Total Measurement Error
% of input error =
ppm of input error =
Example: Computing Total Measurement Error
Assume that a 5 Vdc signal is input to the DMM on the 10 Vdc range.
Compute the total measurement error using the 90-day accuracy
specification of (0.0020% of reading + 0.0005% of range).
Reading Error = 0.0020% x 5 Vdc
Range Error = 0.0005% x 10 Vdc
Total Error = 100 V + 50 V
Range Error Range
(% of range) Error Voltage
0.0004 40 V
0.0004 40 V
0.0004 40 V
Input Signal Level
Total Measurement Error
Input Signal Level
= 100 V
= 50 V
= 150 V
= 0.0030% of 5 Vdc
= 30 ppm of 5 Vdc
100
1,000,000
415
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