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FEC200 DIFF Test

The DIFF test is used to obtain the difference between the results of two other tests already performed. For example:

  • TESTn DIFF 2 3 <1V

In this example the test results will be the difference between the results of test 2 and test 3 (3-2). The sign of the difference will be recorded; however, only the absolute value will be used when testing against the limits.

There are a number of qualifications to observe this test. The results are meaningful only if the scales used on the other two tests are the same and are compatible with the implied units of this test.

MAXX will attempt to reconcile the limit value of this test with the scale of the first of the other two tests. If this cannot be done MAXX will not accept the test.

If there is any doubt about the scales that will be used for the two reference tests, you should add the same estimated maximum expected reading to each of these tests. The typical sequence below will help to illustrate these points.

  • TEST3 VZ 250ľA <12V <13V 20V
  • TEST4 RSURGE 250ľA 400MA >12V 20V T1
  • TEST5 DIFF 3 4<500MV

In this case all three tests will use the 163.83V scale. The respective limits will become 12.99V, 13.00V, 12.00V, and 0.05V.

If it were not, for the 20V item on tests 3 and 4, the 16.383V scale would have been used, which would be ok provided none of the readings exceeded 16.382V.

If the 20V were used on only one test or if just one of the maximum limits exceeded 16.383V, then the scales would be mismatched and the result of test 5 would be meaningless.

The three sequence numbers do not have to be sequential as in the example. The only requirement is that the two reference tests must always be performed before the DIFF test.

The results will be invalid if either of the reference tests is skipped because of a conditional jump.

Incidently, the purpose of a sequence like that above (using the optional type of RSURGE test), would be to measure the effect of the RSURGE test on the VZ at 250ľA.

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Last Updated September 12, 2007
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