Precision Pressure Measurement
The Dwyer Microtector
®
combines the time-
proven principles of the Hook Gage type
manometer and modern solid-state integrat-
ed circuit electronics. It provides an inexpen-
sive means of achieving accuracy and
repeatability within ± .00025 inches water col-
umn throughout its 0 to 2 inches w.c. range.
It is truly a new standard in precision measur-
ing devices.
Principles of Operation
A pressure to be measured is applied to the
manometer fluid which is displaced in each
leg of the manometer by an amount equal to
1/2 the applied pressure. A micrometer
mounted point is then lowered until it contacts
the manometer gage fluid. The instant of con-
tact is detected by completion of a low-power
A.C. circuit. Current for this circuit is supplied
by a 1.5 volt penlight cell feeding two semi-
conductor amplifiers which act as a free-run-
ning multivibrator operating at a frequency of
approximately two kilohertz. Completion of
the A.C. circuit activates a bridge rectifier
which provides the signal for indication on a
sensitive (0 to 50 microamps) D.C. microam-
meter.
2
LOW
PRESSURE
FLUID
LEVEL
OFF
ON
On indication of contact, the operator stops
lowering the point and reads the micrometer
which indicates one half the applied pressure.
By interpolating eight divisions (each being
.000125˝ w.c.) between .001 micrometer
graduations, a total accuracy of .00025 can
easily be achieved. The micrometer complies
with Federal Specification GGG-C-105A and
is traceable to a master at the NIST.
Locating and Opening
Stand the Microtector
®
and case on a firm flat
level surface. Remove cover by releasing the
latches and lifting it straight up. If it is neces-
sary to move the gage without case, handle
only the base plate or clear acrylic block.
(
CAUTION:
Do not handle gage by grasping
meter-electronic package housing Item 7 on
drawing.)
Microtector
®
Gage
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