Agilent Technologies 34970A manual 415

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 Error	Range
Range	Input Level	(% of range)	Error Voltage
10 Vdc	10 Vdc	0.0004	≤	40 ∝V
10 Vdc	1 Vdc	0.0004	≤	40 ∝V
10 Vdc	0.1 Vdc	0.0004	≤	40 ∝V

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 ⋅ 100 Input Signal Level

ppm of input error = Total Measurement Error ⋅ 1,000,000 Input Signal Level

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	= 100 ∝V
Range Error	=	0.0005%	x	10 Vdc	= 50 ∝V
Total Error	=	100 ∝V + 50 ∝V			= ± 150 ∝V
					=	± 0.0030% of 5 Vdc
					=	± 30 ppm of 5 Vdc

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