Master Catalog — Gems Sensors & Controls - H-63

CAPACITANCE TYPE

Gems Capacitance Transducers
-Functional Simplicity
with Structural Sophistication
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Contents	

Page Start

809 Series...................................................................H-64
809H Series...............................................................H-66

High Accuracies
Minimal Mechanical Motion
Broad Range Capabilities
Long Term Stability
High Level Output
Broad Media Compatibility
High Electromagnetic Compatibility
Resistant to Harsh Environments

830 Series...................................................................H-68
856 Series...................................................................H-70
865 Series...................................................................H-72
876 Series...................................................................H-74
890 Series...................................................................H-76

Gems' capacitive pressure transducers are expertly designed
adaptations of a simple, durable and fundamentally stable device...
the electrical capacitor.

5000 Series................................................................H-78
899 Series...................................................................H-80

Principle of Operation
In a typical Gems configuration, a compact housing contains two
closely-spaced, parallel, electrically isolated metallic surfaces, one
of which is essentially a diaphragm capable of slight flexibility under
applied pressure. The diaphragm is constructed of a low-hysteresis
material such as 17-4 PH stainless steel or a proprietary compound of
fused glass and ceramic. These firmly secured surfaces (or plates) are
mounted so that a slight mechanical flexing of the assembly, caused by
a minute change in applied pressue, alters the gap between them. This
creates, in effect, a variable capacitor.

GOLD PLATED
SURFACE

APPLIED FLUID
PRESSURE

}

CERAMIC
WAFER
AIR
DIELECTRIC

}

ELECTRODE
DIAPHRAGM
(CONDUCTIVE
SURFACE)

PRESSURE
PORT

STRETCHED
DIAPHRAGM

REFERENCE
PRESSURE PORT

SENSOR
BODY

Two typical capacitance sensor configurations are
shown here. The capacitor gap is accentuated for
illustration.

PRESSURE TRANSDUCERS

The resulting change in capacitance is detected by a sensitive linear
comparator circuit (employing proprietary, custom-designed ASICs),
which amplifies and outputs a proportional, high-level signal.

The inherent simplicity and ruggedness of this physical configuration,
the fact that all wettable parts are of stainless steel or low-hysteresis
ceramic, and a careful marriage of the mechanical assembly to the
electronic circuitry, all combine to create a transducer that exhibits
uniformly superior performance.

Capacitance Transducer Intro / p1of1 / 29-JUL-19

Visit www.GemsSensors.com for most current information.

H-63
http://www.GemsSensors.com
Master Catalog — Gems Sensors & Controls

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