Electrical – How to connect an oscilloscope to a power supply or function gen.

oscilloscopepower supplyresistorsshort-circuitvoltage

I'm supposed to sketch a circuit for my class but the one thing that has me completely confused is the ground connection.

For example: I have a breadboard with a 10V dc power supply and two resistors connected in series, and I want to measure the voltage across each individual resistor using an oscilloscope.

I know where to connect the signal clip thing, but not where to connect the clip that's supposed to go to ground, which is my main problem.

One of my teachers told me I can connect it directly after each resistor, another told me to connect all the ground clips to the end of the circuit (on the "-" side). My textbook just says in big red letters "CAREFUL NOT TO CAUSE A SHORT CIRCUIT".

Would the circuit be the same if I replace the power supply with a function gen or is there a difference?

I just don't get how grounding works and I've been reading more and more confusing guides online for 5h. I'm about to be graded on my work in 10h, haven't even slept yet. I'm sorry if I'm being confusing. Please help. Thank you.

Best Answer


simulate this circuit – Schematic created using CircuitLab

Figure 1.
(a) Your test circuit.
(b) The right way to connect up a 2-channel oscilloscope.
(c) Connecting the ground clips to two different voltages on the circuit will cause current to flow through the earth connection inside the oscilloscope.


The risk is that you might try to measure the voltage as shown in Figure 1c and attach the two earth clips. If the circuit is a high current circuit then a high current will flow through the red lines and possibly burn up the wiring or PCB tracks inside your oscilloscope.

The correct way is to wire as shown in Figure 1b, take two measurements and calculate the voltage across R1 as \$ V_{R1} = V_2 - V_1 \$.