In my experience, I have found very few a/c pro's who are even aware of the measurement of vacuum in terms of microns. If you have a vacuum meter that will give you microns, it would be very good to see 100 microns.

If the truth could be known, I fully expect that most a/c systems rarely get evacuated much below 1,000 microns. If for no other reason than the fact that many people don't change the oil in their vacuum pumps often enough.

I have given lots of thought to coughing up the money for such a vacuum meter, but other needs keep cropping up diverting the funds.