Test and Measurement Forum

Dear all,

I have a PicoScope 4227 software oscilloscope and I want to ask a question about how to properly connect the Ground Clip from the standard test probe.

I raise the question because on my first measurement attempt I created a short circuit which damaged part of my equipment. I suspect the reason was that the Probe Ground Clip was not properly connected.

I have attached a ppt where I detail the measurement setup that resulted in a short circuit in the first slide, and a second slide where I propose a second measurement setup. I would greatly appreciate if someone could asses whether the new suggested measurement setup is safe.

Best Regards

Daniel

PS: As detailed in the slide, my equipment consists of:
1) A PC
2) a PCI to SDIO card connected to a PCI port in the PC
3) The measurement board which has an SDIO interface.

The part that resulted damaged after the short-circuit was the PCI to SDIO card in the PC.

Dear Daniel,

Thankyou for your inquiry with regard to the Probe ground on your 4000 series measurement application. Sorry you have encountered some difficulties.

Your methodology with the two probe application would work ok providing the ground on the prototype PCI<_>SDIO board is definitely ground and not floating. You need to ensure a reference. However, you would have to take into account accuracy. The 1% stated accuracy would obviously be reduced with a higher voltage range.

There are several options available. One would be to use your original method but ensure the scope is floating i.e run the laptop off its battery only (disconnect power supply -charger) and connect the PCI<_>SDIO card to a SEPERATE PC. You must ensure that there is no path to ground when using your laptop. This works fine for lower level voltages but is not really suitable for higher voltage levels

Another method is to purchase a differential probe this is preferred method especially when using higher voltages. These probes are easy to use and defiantly worth the investment.


http://www.picotech.com/oscilloscope-accessories.html#active

If you require further assistance please do not hesitate to contact me via support@picotech.com

Kindest regards,

Stuart
Technical Specialist

Dear Stuart,

Thanks for your reply.

Please let me ask you another question. In the suggested setup shown in my slide, does it matter if the laptop that the PicoScope is connected to is battery powered or plugged to the power?

Best Regards

Daniel