[amelius]

I've always wondered why modern multimeters don't have a "discharge" option.

I.e., you select the discharge mode, put the probes on a capacitor, and watch the voltage go down, while an internal current limiter makes sure that it happens at a safe rate.

[nickt]

The probes aren’t big enough. That’s why it’s often a big screwdriver and jump lead to earth.

The better option is the Fluke 80K 40.

https://www.fluke.com/en-us/product/accessories/probes/fluke...

[Dylan16807]

Not big enough in what way? A normal probe should be able to handle the distancing and the small current fine. Maybe it would lack insulation but I wouldn't use the word "big" for level of insulation.

[kens]

Typical probes are rated for 600 volts (CAT III), so you'd have insulation rated for 600 volts between your fingers and 30,000 volts, which is kind of hazardous.

Here's a recent Twitter video showing what happens when you combine a flyback transformer and faulty insulation: https://twitter.com/zh1nu/status/1673487720780529664

[Grazester]

Well that might have left a mark. Why would they try to touch it anyway? Even well insulated, I wouldn't try to touch something I didn't need to.

[Dylan16807]

When you combine a running transformer and weak insulation, and also there's no exposed metal where you intend for the current to go. So that probably comes off pretty differently.

But my use of the word "maybe" is more because of overall confusion about the word "big".

[tgsovlerkhgsel]

For lower voltages, some do ("low impedance measurement" or LoZ). Not specifically meant for discharging capacitors but should work for that too.

But this only works up to the voltage the multimeter is rated for (i.e. usually 300 or 600 V). If you wanted to make it safe to put 30 kV across the multimeter, it'd have to be designed with sufficient insulation etc. for that.

[formerly_proven]

An electrician's voltage tester (the not-fake ones) can be used for this, for off-line filter caps anyway. 30 kV, not so much.