Earthing

It is very easy to leave the meter in the wrong setting,especially if in a hurry.

I was using my fluke to record Min/Max on a ultrasonic flow meter,and left it turned on during the night,testing for intermittent problems.

It was the dog days of summer,and the weather was very hot and humid,and of course,that was when my home A/C unit quit.

I hurriedly retrieved my meter from the shop and checked for voltage at the compressor,"Boom" the lights went out in the whole house.

At first I was puzzled,then I looked at my meter,the leads were still in the amp setting....Dang it!

Even after more than 30 years of troubleshooting,I had made this stupid mistake.

The meter was not destroyed,it had blown the 10 amp KTK fuse and survived with no internal damage.

Gotta love those Fluke Meters!..it had tripped the 100 amp main and did not even spark at the meter leads.

The meter was rated for explosive atmospheres,and it did it's job very well indeed.

Anyway,it was a bad compressor,and I had to replace it,pull down the system,purge with nitrogen, install a new filter and recharge with Freon..it was #22 back then.

Haste makes waste,as the saying goes.

Where I am from, the L or line on AC is the hot lead. We put our meter ground lead on neutral.
Are you using AC powered measuring equipment? Many more situational details would be needed for a meaningful solution.