I've read the answers from a similar question but didn't find it to answer my question.
I'm trying to make a phase control circuit to control an AC motor, and would like to monitor the output.
The input can sometimes be normal mains AC, but other times from a battery/230VAC inverter. The inverter seems to have two opposing hot lines (e.g. -115VAC + +115VAC = 230VAC) rather than neutral/hot wire.
Can I measure directly?
I've got a DSO1054Z, which has a maximum input voltage of "CAT I 300 Vrms, CAT II 100 Vrms, transient overvoltage 1000 Vpk With RP2200 10:1 probe: CAT II 300 Vrms".
I understand from this article that CAT II would be recommended for a standard wall outlet.
The oscilloscope is only rated at 100 Vrms CAT II.
So I assume the answer is: no
Can I measure through a voltage divider?
I'm considering using this circuit to reduce the voltage (from 230 VAC to 2.27 VAC). Since there are two hot wires, the voltage divider has to go in both directions. Also, the high resistance should reduce the short-circuit current to about 0.23mA, greatly reducing the outcome of a worst-case scenario.
I'm assuming the answer is: yes, the probe will now be safe.
I'm thinking to use the differential measurement on the oscilloscope to add the two signals.