Setra Systems 761 Operating Instructions Manual - page 3
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1.0 Introduction
Setra’s Model 761 capacitance manometer is a temperature compensated,
vacuum manometer designed for accurate and repeatable vacuum mea-
surements.
The Model 761 operates from a 13-30 VDC power supply and provides a
0-10 VDC or 0-5 VDC signal output that is linear with pressure and indepen-
dent of gas composition. It is configured with a 15 pin D-Sub with “plug
and play” industry standard pinouts. The Model 761 is pin for pin compat-
ible with other competitive capacitance manometers. Superior EMI/RFI
performance is achieved by the use of a metal case in conjunction with
surge and ESD suppression components and RFI filtering on the inputs and
outputs. Inconel® is used for all wetted materials for compatibility with cor-
rosive gases. A wide range of pressure/vacuum fittings are available.
The high accuracy pressure sensing element used in the Model 761 has
been developed from Setra’s patented variable capacitance sensing tech-
nology. An electrically isolated, centrally located feed through assembly
supports a circular electrode in close proximity to the back surface of the
diaphragm. Together, the electrode and diaphragm form a variable capaci-
tor within a small reference vacuum chamber. As the pressure increases,
the diaphragm deflects and the gap between the electrode and diaphragm
decreases, causing an increase in the capacitance. This change in capaci-
tance is detected and converted to a highly accurate linear DC electronic
signal by Setra’s unique custom circuit.
Excellent zero stability and thermal insensitivity are achieved through
the patented sensor design. The Model 761 sensor contains no fragile or
complex parts as found in ceramic based capacitance manometers. The all
welded construction eliminates stability issues inherent in other designs
due to frictional contact between dissimilar materials.
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US Pat. 8,893,555