Hello. I have just bought a digital oscilloscope. I just wanted to ask a safety question regarding the ground wire.
I am using a bi polar power supply. There are +15, +12, +5, 0v, -5, -12, -15 outputs. There is no continuity between the 0v and the earth pin on the plug or between either of the voltage outputs and the the 0v. The resistance between the power rails and the 0v is between 0.8k and 0.9k.
Let's say I have the 0v and +12v powering an Arduino then the Arduino +5v and ground outputs powering a circuit on a bread board. Is it safe to put the ground clip from the oscilloscope into the ground rail on the breadboard?
Let's say I have -12, 0v, +12 powering a circuit on a breadboard. Do I just attach the oscilloscope ground clip to the 0v on breadboard or even directly to 0v on pcu.
Connect it to a ground close to the point you are measuring.
If unsure probe the intended ground point with the probe tip to confirm it is at ground potential
first. Then if its at or very close to 0V, connect the ground clip and move on to the measurement
you want.
Remember to have DC coupling selected before checking for ground.
Congratulations, that will be one of your top pieces of test equipment, the best is between your ears. One important thing to remember is if the scope plugs into the power mains the ground internal to the scope, probes, and power line ground pin are connected. Also you have coupling to think about AC or DC. If you are looking at DC voltages or an ac signal with a DC offset you can use AC coupling to eliminate the offset from showing. The switch that has AC/DC coupling also has Gnd, switch it to that to zero your scope and set the traces to where you want them. Tektronix, LeCrox, HP and others have a lot of application notes that will help you, it would pay to spend a few days reading them. Just a hint it helps if you have an idea of what you are looking for.