The Indicator Probe (IP) is a special use probe, which shows the amount that standard probes are deflected in a test fixture. The Indicator Probe's plunger does not return to its original extended position after deflection. Indents in the side of the probe tube interfere with the free motion of the plunger and hold it at the position of maximum deflection. The Indicator Probe may lose its ability to remain in the deflected position and should be replaced after approximately 5 deflections.
Indicator Probes are identical in external dimensions to their standard counterparts. The entire plunger is unplated, so that it can be easily distinguished from a standard probe. Indicator probes are not intended for use as electrical contacts.
Remove the standard probe from the socket.
Install Indicator Probe. When Indicator Probe is installed into the socket the plunger will stick down.
Extend Plunger. Hold the top of the probe tube in the socket with tweezers while pulling up on the plunger with another set of tweezers.
Reassemble the fixture and cycle once. The plunger will remain in the deflected position, showing its position when the fixture is actuated.
Measure the difference in height. This is the probe stroke in which the fixture actuated while in production
Instructional video on how to measure probe stroke in a fixture