I just bought my first analog oscilloscope (GoldStar OS-7020A) and noticed it has a port on the front labeled "ground". What exactly is this port for?
I thought it might be for plugging in a ground clip for probes that don't have one included, but there are two channels and only one ground port, so I'm not sure. Is it simply for providing a convenient ground connection for other devices?
Could I, for example, attach my anti-static wrist strap to it? Would the oscilloscope have to be on for that to work? (Electronics newbie here, so please forgive me if this is a stupid question.)
Best Answer
Most oscilloscopes have a safety ground. This connects to the earth ground on the plug and also to the case. The thinking is if you wire it up wrong worst case you trip the GFI/RCD instead of shocking yourself or damaging the instrument.
As an oscilloscope is usually a bench instrument it is not isolated from the mains. You can use an isolation transformer, but this is not recommended, as it removes this protection leaving the earth ground floating.
Tektronix sells an oscilloscope which has fully isolated inputs, I don't know of any other models. It is significantly more expensive to add high speed isolation circuitry. Usually it means the whole analog and acquisition side must be isolated.
The ground should always be connected to your circuit's ground or you will get strange behaviour. Trust me. I've spent hours looking at a trace wondering where the noise was coming from, just to find I haven't properly connected the ground.