PXIe-4137 voltage clamping

[patrick.chaopricha]

We are currently evaluating PXIe-4137 SMU module.   We like the low noise measurement capability and the current output range of 1A.  However, we are concerned about the 200 VDC output capability.   During a normal use, we would never go over 20VDC, but if the module somehow got set by accident to 200VDC that could be lethal for somebody touching any output contacts.

Does the module have a hardware voltage limiter that we can set so that it won't ever put out more than 20V?  I don't trust the remote set to gaurantee the safety since somebody could accidently enable the 200VDC output.

Thanks,

Patrick

[stephencox]

The safety interlock limits the output to +/-40 VDC when open according to the manual, but I am sure your safety office would disapprove of using this as an intentional control on the output voltage.  NI makes it pretty clear in the manual that they don't consider it safe to use this SMU in an environment in which the leads are exposed.  Could you cover the leads with something that is interlocked to the SMU so that you're still using the interlock correctly but also using it to limit the voltage output to a non-lethal level when the cover is removed?

[patrick.chaopricha]

Thanks for the reply.   Doesn't the interlock also stops any output from being on when it's opened?   So we can't probably use it as a voltage limiter even if we want to.  You are definitely correct that the safety officer will not let that fly.

Unfortunately the SMU modulel connects up to a metal probe for testing and therefore it's not really a sealed system.  We do make manual adjustment to the probes occasionally and I definitely don't want to take any chances electrocuting the operator working on the system.

It doesn't sound like we can use this module safely without taking some chances of electrocuting somebody.   I'll have to look for a different module to use.

[stephencox · Accepted solution]

I haven't set these up yet, so I can't test it myself.  But the manual says "with the safety interlock terminal open the output voltage level/limit is limited to +/- 40 VDC, and protection will be triggered if the voltage measured between the device HI and LO terminal exceeds +/-(42 Vpk +/-0.4 V)."  My reading was that it would function in low voltage mode without a safety switch connected.  Beyond that, it looks like all the limits you can set are done in software.

[patrick.chaopricha]

That's awesome. I need to find the manual since I couldn't locate one online but I thought I saw one in the box. I'll test it out!