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PXIe-4113 Supply, Avoid voltage overshoot when sense is open

Hi there, 

 

I use the PXIe-4113 as a supply for several DUT's. The supply to each DUT can be switched on and off individually over high side switches controlled with a relay card (PXI-2571), the sense of the suppy is switched as well with the relay card to the selected DUT.

 

That all works just fine for me, as long the relays do what they should do. But since the relay card is mechanical, I have to expect that a relay does not close properly, has a hang, weak contact or something else.

 

One example would be a damaged relay or hi-side switch which controlls the DUT supply:

If the supply to the DUT is open due any kind of error but the sense is connected to the DUT, my supply may drive the voltage up to >10V. The sense will be pulled to GND over the DUT.

Well that's no problem you might think, because this voltage is not connecte to the DUT, right? Yes, but if this is caused by a bad relay contact and the relay suddenly starts to make contact again, I have the >10V on the DUT which will be destroyed even it is for a very short time before the supply sets back to the defined voltage.

 

I would be happy if there is any way to avoid this in the software because otherwise I would have to make some kind of protection circuit in hardware.

 

Any idea would be welcome.

Best regards

 

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Hi,

 

for some modules you can use the Switch Health Center. With this Software you can check, if the Relais are closed when there is no output connected.

 

 

NI Switch Health Center - National Instruments
http://www.ni.com/white-paper/11971/en/

 

In this Link you can find the supported modules, but the PXI 2571 is not included.

 

Which NI Switch Modules Support Resistive Self Test and Temperature Monitoring? - National Instruments
http://digital.ni.com/public.nsf/allkb/C330C9CA3295B58F86257DAF00706538

 

Best regards,

Lucia Nagl

 

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Hi,

 

In your case I would program it to set the voltage to the maximum voltage of the DUT without the sense active, measure the current to the DUT and if that is OK switch on the sense inputs. 

Depending on the current of the DUT you could also protect the DUT with zenerdiodes.

 

 

Kees

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