McLeod Gauge 0-60 Micron
A McLeod gauge is an absolute
pressure standard to which many other vacuum gauges are calibrated.
It will accurately measure the total pressure of non-condensable
permanent gases (i.e. hydrogen, nitrogen, oxygen, etc.) in a vacuum
system, but will not correctly measure condensable vapors if present.
Many condensable vapors will be condensed during compression of
the gas sample in the capillary tube and not contribute to depression of
the gauge liquid.
The calibration of the gauge
for non-condensables is based upon Boyles/Charles physical chemistry gas laws
P1*V1 = P2*V2 and therefore measurement of the volume of the glass bulb
and the volume per unit length or bore of the capillary tubes is made
with high precision. It is
based upon dimensions during manufacture so that once it is correct,
very little can go wrong to change its calibration, and so it can be
reliably used as a reference standard.
If condensable vapors may be
present while calibrating a vacuum gauge against the McLeod gauge, then
a liquid nitrogen cold trap should be used to ensure that only
non-condensables are being measured.
The HyVac Oil McLeod Gauge
consists of a borosilicate glass cylinder mounted on an aluminum base.
The bottom of the cylinder acts as a reservoir for 6cc of mercury
covered by 100cc of a special low vapor pressure oil.
Within this cylinder is positioned a glass bulb with two
capillaries, one of which is attached to a metal sleeve with a small
magnet at the end. A
rectangular scale with graduations from 0.1 to 50
microns (millitorr) is attached to the two glass capillaries.
This internal plunger assembly with scale can be raised or
lowered into the liquid reservoir by use of an external ring magnet
which is magnetically coupled to it.
As the ring magnet is slid up or down on the exterior of the
hollow cylindrical metal tube at the top of the glass cylinder, the
internal plunger moves in unison without any relative movement between
the two. O-rings are used for sealing
the stainless steel and aluminum plug at the glass cylinder
The HyVac Oil McLeod Gauge has the following features
when compared to other McLeod gauges:
Because the 6cc of mercury are covered by 100cc low vapor pressure
diffusion pump oil, the amount of mercury vapor exposed to the
environment is vitually negligible compared
to a conventional mercury McLeod gauge, thus avoiding the mercury
vapor health hazard.
The quantity of oil required to be outgassed is small which reduces the
Better definition between readings in this range than mercury McLeod
Light weight and compact.
|HyVac Part No.
||0-50 microns (millitorr)
||Including 6cc of
| Weight of Gauge
||5.5" x 7.5" x 19"
Extended base for added stability.
Shutoff / Isolation valve with valve support. This option isolates gauge
from System / pump. Includes
an extended base and vacuum hose.
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