sensing presence off uut using switch

[david_jenkinson]

Hi,

I have an application where I'm going to be designing a multiple UUT tester.  The UUT's themselves will be mounted on plates which individually install by setting them on pins in the tester prior to testing.  I want to sense the presence of these plates, to know how many uut's are loaded (up to 9).  Does anyone know of a model of switch, either mechanical or optical, that could work in this case, that they've had success with (reliable)?  The smaller the profile the better.  I have NI 6518 cards already from another project so preferrably one that will integrate with it's required 24 v level, but that can be worked around also.  Thanks for any insight.

Cheers,

David J.

[SnowMule]

Use a digital line with an internal pull-up resistor? (6008, 6501)

Stick a pin on another ground point on the board, use that to detect a DUT on the fixture.  Ground on the PCB pulls the DI line low, read that in LabVIEW.