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 ilustrates the
range error applied to the meter’s 24-hour dc voltage specification.
Range Input Level
Range Error
(%of range)
Range Error
Voltage
10 V 10 V 0.0001
≤ 10 µV
10 V 1 V 0.0001
≤ 10 µV
10 V 0.1 V 0.0001
≤ 10 µV
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.
% of input error =
Total Measurement Error
Input Signal Level
∗ 100
ppm of input error =
Total Measurement Error
Input Signal Level
∗ 1,000,000
Total Measurement
Error Example
Assume that a 5 Vdc signal is input to the meter on the 10 Vdc range.
To compute the total measurement error using the 90-day accuracy
specifications: ±(0.0020% of reading + 0.0004% of range).
Reading Error = 0.0020% ∗ 5 V = 100 µV
Range Error =
0.0004% ∗ 10 V = 40 µV
Total Error =
100 µV + 40 µV = ±140 µV
% of input error =
± 140 µV
5 V
∗ 100 = ± 0.0028% of 5 V
ppm of input error =
± 140 µV
5 V
∗ 1,000,000 = ± 28 ppm of 5 V
Chapter 8
To Calculate Total Measurement Error
282
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