Re: 2465B leaky voltage


Chuck, thanks for laying out, step by step, what I was summarising.

The 113V reading is about what you would expect using a DVM with high (10M) input resistance with the scope's ground disconnected. It's simply the pair of Y caps in the filter acting as a potential divider. I don't know the value of the Y caps but from memory the maximum current that's allowed to flow from live to ground is about 250uA for a Class II (double insulated) appliance, somewhat more for a Class I (grounded) appliance. Even 250uA will give you a tingle, I've felt this many times when handling kit that isn't grounded.

If 1 of the Y caps in the filter was faulty I would expect the voltage reading to be either close to zero or close to full mains. The fact that it's close to half mains strongly suggests that the filter is OK and the scope's ground is missing. Also if one of the y caps was faulty I would expect a 30mA RCD (aka GFI) to trip. Assuming your lab is protected by one of these, and I really hope it is.

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