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SECTION III
Principle of Operation
The Model HPT 100, Ultra High Purity Pressure Transmitter series is a state of the art
family of pressure transmitters based on metal thin film technology. This advanced
technology allows for stable and accurate measurements throughout the gas distribution
system. Pressure on a Hastelloy diaphragm is sensed by a sputtered metal thin film
wheatstone bridge which is isolated from the diaphragm using glass. The stability of this
technology allows the user to not have to make frequent adjustments of the zero or span
potentiometers..
The signal from the sputtered element is amplified using low noise operational amplifiers
allowing conversion to 4-20 mA or 0-5 Vdc configurations. The use of EMI and transient
protection components allows operation to continue in noisy electrical environments and
provides durability demanded by semiconductor fabrication facilities. The circuit is fully
temperature compensated to allow operation indoors or outdoors. The signal conditioner
circuitry can be easily removed and replaced with another standard circuit board,
minimizing process downtime.
Adjustments
An access cover is provided to allow for zero or span adjustments, and a diagnostic shunt
feature allows a quick check of the transmitter. The zero and span potentiometers offer at
least 5% full scale adjustment. Your transmitter has been calibrated in the factory and
usually the only adjustment is to make a slight re-adjustment of the zero upon coupling
to a pressure line. The span should not normally have to be adjusted, except when
making range changes. After making an adjustment, use a tool to tighten the adjustment
cover. This will provide optimum sealing in moist or dusty environments. Caution is
advised as over tightening can strip the cover or adjustment plug threads or damage the
sealing O-ring.
pg. 2-6
pg. 3-1
OPERATION
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