User`s guide

339
Chapter 8 Specifications
To Calculate Total Measurement Error
4
8
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.
% of input error = x 100
ppm of input error = x 1,000,000
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).
Range Input Level
Reading Error
(% of reading)
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
Example: Computing Total Measurement Error
Reading Error = 0.0020% x 5 VDC = 100 V
Range Error = 0.0005% x 10 VDC = 50 V
Total Error = 100 V + 50 V= ±150 V
= ±0.0030% pf 5 VDC
= ±30 ppm of 5 VDC
Total Measurement Error
Input Signal Level
Total Measurement Error
Input Signal Level
34970A Refresh UG.book Page 339 Wednesday, February 17, 2010 12:34 PM