Multifunction Calibrator
Full Verification
51
measurement as well. Some organizations also elect to call this a conditional fail
because there is still a possibility that the measurement is in tolerance. Most
organizations consider this an out of tolerance result because although the value
may exist anywhere with the interval of the measured value plus and minus the
uncertainty, the best estimate of the value is the measured value.
RDS Method
Another guardbanding method that is the root difference of squares method. The
test limit for this method is defined as:
This method makes a less aggressive guardband while still providing sufficient
confidence in the measurement result for most quality standards. The
determination of pass and conditional pass is generally used for this method in
the same manner as the ILAC G8 method. The RDS method is used widely at
Fluke Calibration and many other companies as a reasonable approach to
ensuring confidence that the verified Product meets its published specifications.
This is not an all-inclusive list of guardbanding strategies. The method selected
must meet the quality system requirements of the owner of the Product being
calibrated. The best uncertainty attainable at some test points can be relatively
large as compared to the specification. Fluke Calibration recommends that when
making conformity assessment decisions of in or out of tolerance to published
specifications during performance verification, the uncertainties of measurement
should be evaluated and appropriate guardbanding rules should be applied to
have sufficient confidence in the calibration results.
Resistance Verification Test
The subsequent tests check every resistance value from 0 Ω to 100 MΩ. For
0 Ω,1 Ω, and 1.9 Ω an 8508A measures the resistance directly. For 10 Ω to
100 MΩ the 8508A is used in a transfer method where the Digital Multimeter
(DMM) first measures a resistance standard and then measures the Product. The
Product resistance value is then calculated. Use Tables 5 and 6 for the test
record. Table 4 lists the required equipment.
Table 4. Required Test Equipment
Equipment Model
Fluke Standard Resistors
742A-10, 742A-100, 742A-1k, 742A-10k, 742A-
100k, 742A-1M, 742A-10M and a 100 MΩ
Standard
Fluke DMM Fluke 8508A
Low Thermal Cables 5730A-7003
Special Shielded Cable See “Verify 100 M Ω” for details
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