Neat back-EMF experiment

[BrianG]

Ok, I was bored. In between projects so I decided to hurt myself.

I made a quickie oscillator circuit out of a 555 timer IC with a frequency of ~2Hz and a duty cycle of ~80%. Easy enough. So, I decided to hook the output of that to a small relay that is hooked to a 7H inductor (yeah, that's 7000mH). Then I hooked my Fluke meter to the inductor output and powered up the circuit with 6v. However, when I try to get a back-EMF reading of the inductor, it "reboots" my multimeter, which has a max voltage of 1000v. Hmm, I tried a voltage divider, but something's not right.

Sooo, I wisely () decided to hold the probe ends so I can use my "manual measurement" method. All I can say is OUCH! My hand is still kinda numb typing this.

Anyone know how to compute inductive kickback using the scenario above. Been a long time since I played around with the formulas and a quick net search didn't turn up with the info I want. And I'm too lazy to search more.