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Absolute
pressure measurements become necessary for hydrocarbon refining processes, edible
oil deodorization and many other high vacuum stripping or drying processes.
We
have in stock the following absolute
vacuometers (or presometers):
 Bennert vacuometers:
is an U-Tube vacuometer having one blind tube leg, evacuated and
filled with mercury. The open
tube leg is connected to the
vacuumed system to be measured where the absolute pressure is.
Standard range is 0 - 160 Torr
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 Mc Leod vacuometer: is a portable instrument
ideal to check plant measurements and laboratory calibration of plant
absolute vacuometer.
The
glass test tube is normally positioned with the measuring capilary
horizontal. To take a
measurement of the absolute pressure, the ensamble is rotated 90°. The turn pushes the
mercury to compress a fixed volumen of
the gas in the capilar, now vertical.
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 Thermopile vacuometer: The system includes a vacuum gauge tube with a noble metal thermopile,
a bridge circuit and a galvanometer.
A low voltage AC heats the thermopile in order to generate an EMF.
A change in pressure and density of the gas colate a change in the
heat transferred to the gas cooling the thermopile, as its temperature
changes, so does the DC
output that passes to the galvanometer
whose scope, non
linear, is graduated in mb.
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 Capsule vacuometer: The gauge pressure element is an evacuated capsule.
The pressure to be measured is applied to the hermetic case where
the capsule constitutes the zero pressure datum.
The movement of the capsule when the pressure changes is amplified
and trasmited to the pointer via mechanical
linkage and gears. The
mechanism is carefully balanced to minimize pointer positioning error.
Absolute
pressure readings are independent of the atmospheric pressure variations.
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 The well vacuometer
is a relative vacuum meter (referred to atmospheric) pressure.
The head variation of the level in the well is of negligible
magnitude. The vacuum can be
read directly on a single scale, instead of substracting two readings, as
happens in a U-tube manometer. This
is a useful laboratory instrument to check Bourdon type vacuometers.
The
standard range is 0-800 mmHg.
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Traps: Traps
are intended to protect the vacuometers from the process gases, dirt and
humidity condensed in connection lines. The body is constructed of cast aluminium,
a glass cover is fitted to enable visual check of the inner part or
liquid level. The traps may include the operation valves.
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