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value measured must be above the SUTV. For the closed condition, the measured value
must be below the SLTV threshold. It is important to set these threshold values even if
bounce testing is not performed. If improperly set, the switch may fail the initial state
condition test. This test is performed whenever contact resistance testing is performed.
Bounce testing can only be performed if contact resistance testing is performed. It
makes no sense to test bounce if final contact resistance is not proper. To measure
bounce implies that contact resistance will be measured. To measure contact resistance
implies that the initial state condition of the contact is tested and appropriate.
Test Times
The LCTS controls the time of each cycle of the switch. There is independent control of
both the up and down stroke of the air cylinder. To simplify discussion, only the down
stroke of a normally open switch will be discussed. All operations and setup applies
equally to the up stroke, and testing the closed condition of the contact inverts the
tolerance and threshold directions. Figure 8 illustrates a typical down half cycle.
Down Time
Cylinder
Contact
Plunger & Switch Transition
Contact
Bounce
Contact
Stabilize
Check Initial Contact State
Measure Final Resistance
Software Monitors Contact
Figure 8.
Typical Down Stroke of NO Switch Type
This half cycle begins with a measurement of the initial state of the contact. It should be
open to pass the test. The measured value must be greater than the SUTV of the
bounce thresholds to pass. If not, an
Initial Contact Failure occurs. If the contact is not
being measured for this half cycle, then no contact measurements are made and the
down time is fixed to the
Maximum Down Time value programmed into the configuration.
Once the test of the initial condition is complete, the pneumatic control valve is actuated
to apply pressure and drive the air cylinder down. Immediately software begins
monitoring the switch contact for state transitions above and below the set thresholds.
The pressure builds behind the air cylinder and the plunger begins to move. This
