Measuring for DC Offset On 240 Volt Single Phase Supply.

[Roger Ground]

Hi.
How do I measure for DC offset on a 240 volt single phase supply, live, neutral and earth, using a handheld battery operated oscilloscope and a true rms multimeter?

What other interference on the 240 volt supply can I measure, and how, with these instruments?

Thank you.
Roger

 

[3125b]

You can measure DC directly with the multimeter, make sure the meter and the leads are rated appropriately (for mains use minimum CATIII).

I would not recommend you attempt to measure it with a scope if you ask this question. The appropriate setup depends on the model, do not connect it directly to mains voltage without attenuation! Use only appropriate accessories.
Most cheap oscilloscopes have 8-bit ADC's (though it is common to scale that up to 32-bit and falsely advertise it as such), they do not have the resolution for high-accuracy measurements. The AC amplitude is sqrt(2)x240V=339V, whereas the DC component will almost always be below 1V, most likely ~0.1V.
Your local transformer supplies only AC of course (with some distortion), certain appliances can cause a small DC offset. In a normal household this would be inconsequential.