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5560A/5550A/5540A
Service Manual
Example: the 1 year, 99 % confidence specification for the 5560Aat 1 mA, 1 kHz is 0.025 % + 100 nA.
Multiply the relative specification by the output value to convert the relative specification to the same
measurement unit as the floor specification:
1 mA x 0.025 % = [(1 x 10
This formula makes the combined absolute specification 250 nA + 100 nA = 350 nA
The specification limits at 1 mA would be 0.999650 mA to 1.000350 mA
Applying Guardbands to Specification Limits
The expanded uncertainty of measurement must be determined by each laboratory that calibrates the
Product. Even if the procedures for performance verification in this manual are followed completely,
there are different sources of uncertainty due to traceability, environment, electrical cabling, electro-
magnetic interference, uncertainty of the reference standards used, and operator influences that are
unique to each calibration laboratory. These must be accounted for their individual situations, so it is
not possible for Fluke Calibration to estimate uncertainty for all user calibrations.
Those doing the calibration of the Product can verify to 99 % confidence limits, 95 % confidence limits,
90-day, 1-year specifications, or 2-year specifications. While the calibration procedure included in this
manual is applicable to testing every test point, the uncertainty from the calibration process as
compared to the specification limit varies and can require further consideration of measurement
decision risk.
Some quality systems require adherence to particular rules for measurement decision risk when
making claims of compliance with a specification.
Examples of decision rules are:
1. The ratio of the specification tested to the expanded uncertainty of measurement (often referred to
as the Test Uncertainty Ratio) must be greater than 4:1.
2. The probability of a false accept risk must be less than 2 %.
3. The Product cannot be determined as meeting specifications unless the measurement at the test
point is less than the value of the specification minus the expanded uncertainty.
To comply with these decision rules, establish a guardband for each test point. A guardband creates a
zone that is less than the specification limits, and if the measured value obtained from the calibration is
not in the guardband area, the level of measurement decision risk is sufficient. The inner edge of the
guardband is the test limit for the calibration shown in Figure 2.
10
-3
-2)
) A x (0.025 x 10
] = 2.5 x 10
-7
A = 250 nA
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