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8-4
Limit Tests and Digital I/O
klqb
Application — A typical application for a 2-stage limit test is to sort a batch of DUT
according to tolerance. For example, you may want to sort diodes (all having the same
nominal value) into three groups, 1%, 5%, and >5%. The limits for Limit 1 would be the
5% tolerances and the limits for Limit 2 would be the 1% tolerances. If a diode passes both
tests, it belongs in the 1% group. If it passes Limit 1 but fails Limit 2, it belongs in the 5%
group. If it fails both tests, it belongs in the >5% group.
Figure 8-3
Operation model for limit test
Start
Measure
DUT
Limit 1
Test
No
Pass
?
Yes
Limit 2
Test
No
Pass
?
Yes
Display
"OK"
End
Display messages indicate which test or tests have failed, but they do not
indicate which limit (HI or LO) has failed. When using remote operation, you
can determine which limit failed by reading the measurement event register. See
Ref C for the FAIL? commands in
Relative (Rel), mX+b, m/X+b, and log can be used with limit testing. The tests
will be done on the result of the math operation (not the input values). These
math operations are covered in
Model 6487 Reference Manual
Display
"L1"
Display
"L2"
Table 8-3 on page
Section
5.
8-18.
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