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Section 3
Testing
Test Methods
The LCTS uses a single chip microprocessor for control and test measurement.
Integrated into the design is nonvolatile data storage. This allows the unit to be stopped
and powered down without losing the configuration information or accumulated test data.
The LCTS does not retain test results for each test cycle. Instead, it keeps a running
value for the minimum and maximum contact value measured.
If enabled, the LCTS measures the contact resistance and checks it against the
minimum and maximum tolerances. It also keeps the maximum bounce time measured.
Bounce can be optionally enabled. Typically, bounce is desired to be as small as
possible. Thus, the minimum bounce time is assumed to be 0.0 usec.
Down
Up
Cylinder
Down Half Cycle
Up Half Cycle
Initial
Contact
State
Figure 5.
Initial Contact State Testing
When any single contact measurement is made, the value is checked against the
minimum and maximum contact resistance tolerances. If the value falls outside this
range, the contact measurement is considered to have failed. Similarly, the bounce is
checked to be sure it is less than or equal to the maximum bounce time tolerance.
Exceeding this tolerance value is also a failure. There are a total of 4 possible failures
for each test half cycle. The 3 specified above and the initial state of the contact (Figure
5). The initial contact state is a go / no-go test to be sure the switch contacts are in the
proper state before the air cylinder even begins to actuate. For example, with a
normally-open switch (NO), the contact is expected to be “open” before the air cylinder
presses down on the switch. This test is performed with the same thresholds that the
bounce test uses (to be described shortly). There are up to 4 failures possible on the
down stroke of the air cylinder, and another 4 on the up stroke. All operations of the
LCTS are symmetrical between the up and down stroke half cycles.
The LCTS does report the last up and down contact measurements and bounce times
when queried. These values are displayed on the application screen and are stored in
the test result file. It is possible to set the LCTS to stop after each test cycle. This allows
each test cycle to have its data recorded. However, the operation will not be smooth due
