Oh. Here's your fix:

A longish piece of green grass. Hold it by one end, then slide it on the fence wire like the grass was a violin bow, getting your fingers closer and closer to the fence. At some point you notice a pinging, or your fingers are touching the fence.

You can use this to gauge, very roughly, how powerful the charge is at that point.

I never said it was pleasant. But sometimes some types of pain are the right kind of pain.

Example of the opposite: when I'm swapping a switch in my old-ass house, sometimes I'm too lazy to turn off the breaker. When I inevitably shock myself, I say "dammit" because I'm trying to concentrate, not discover my preteen proclivities.

Edit: well slap me silly and call me a liar, I literally said the words "some pain can be pleasant." I blame this error on undeserved confidence and complacency.