Technical data
38 34980A Service Guide
2 Specifications
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.
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.
Example: Computing Total Measurement Error
Assume that a 5 Vdc signal is input to the DMM on the 10 Vdc range.
To compute the total measurement error using the 90- day accuracy
specification of ±(0.0020% of reading + 0.0005% of range).
Range Input Level Range Error
(% of range)
Range Error voltage
10 Vdc
10 Vdc
10 Vdc
10 Vdc
1 Vdc
0.1 Vdc
0.0004
0.0004
0.0004
40 V
40 V
40 V
% of input error =
Total Measurement Error
Input Signal Level
-------------------------------------------------------------
100
ppm of input error =
Total Measurement Error
Input Signal Level
-------------------------------------------------------------
1 000 000
Reading Error 0.0020% x 5 Vdc = 100 V=
Range error = 0.0005% 10 Vdc = 50 V
Total Error = 100 V + 50 V = 150V
= 0.0030% of 5 Vdc
= 30 ppm of 5 Vdc