This is a copy of some info from a pump manufacturer's site. FWIW

Pressure Rise Test

We previously mentioned that the only difference
between deep vacuum and the methods of the past is
that we can measure what we have done. This is called
the Pressure Rise Test.
When the sensor reads between 300 and 400
microns,
DV-29 Method. Blank-off the high and low side ball
valves attached to the system.
General Hookup Method. This includes using
copper tubing or metal hose to the high and low side.
Close blank-off valve on the pump. This will isolate the
gauge from the pump.
Wait for at least 5 to a maximum of 20 minutes to
allow system pressure to equalize. The reading you see
at the end of this test will be very close to what you
actually have in the system. A rapid rise during this test
to atmospheric pressure indicates a leak, while a slower
rise to around 1500 microns indicates moisture is
present.


There are many evacuation level recommendations
including the statement “evacuate the system to below
200 microns.” This should not be considered. Note we
say “system” because it is possible to evacuate piping or
some component other than the compressor to below
this level. Refrigeration oil has a vapor pressure and by
going below 200 microns, you will degas particles of the
refrigeration oil. By changing the makeup of the oil, it will
no longer be a true lubricating oil.
Printed in U.S.A.
ã2004 J/B Industries Inc.

__________________
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)