Setra all products Selection Guide
Industrial Sensing
Product Selection Guide
Setra Systems, Inc. was founded in 1967 by brothers Dr.Y.T.
Li and Dr. S.Y. Lee, both professors of engineering at the
Massachusetts Institute of Technology and co-developers
of the variable capacitance transduction principle.
Building on this heritage of innovation, we continue to
design and deliver premium sensing devices for many
diverse applications and industries — innovating solutions
for HVAC & building automation, industrial OEM, test &
measurement, and critical environments.
Setra’s technology
Gold plated surface
Ceramic wafer
Air dialectic
Diaphragm
(conductive surface)
Setra is part of the Fortive group of companies, a diversied
industrial growth organization with 24,000 employees
worldwide. The Fortive Business System (FBS) is the
cornerstone of our culture and our ultimate competitive
advantage. It drives every aspect of our work, our strategy
and our performance. We use FBS to guide our decisions,
measure how well we execute and develop innovative ways
to do even better.
Variable capacitance
In a typical Setra conguration, a compact housing contains two closely
spaced, parallel, electrically isolated metallic surfaces, one of which is
a diaphragm capable of slight flexing under pressure. The diaphragm
is constructed of a low-hysteresis material such as 17-4 PH SS or a
proprietary compound of fused glass and ceramic (Setraceram).
Sensor body
Advantage of
capacitive
sensors
These rmly secured surfaces (or plates) are mounted so that a slight
mechanical flexing of the assembly, caused by a minute change in applied
pressure, alters the gap between them (creating, in effect, a variable
capacitor).The resulting change in capacitance is detected by a sensitive
linear comparator circuit (employing proprietary custom designed ASICs),
which amplies and outputs a proportional, high level signal.
Better for applications that are susceptible to over-pressurization
—
Very good hysteresis, linearity, stability, and repeatability, in
addition to static pressure measurement capability
—
Excellent accuracy in low pressure ranges – as low as 1 PSI.
Providing you the right solution for any application
Capacitance technology
Thin lm strain gauge technology
-14.7 0 15 75 250 1k 10k 32k 250k PSI
Sensor type Measuring principle Best avail. accuracy Pressure ranges Max. temperature ranges
Variable capacitance
Thin lm
Fixed electrode with moving diaphragm
linearized over temperature through ASIC
Wheatstone bridge with integrated temperature
compensation; resistors in compression or
tension, then linearized through ASIC
±0.05% FS
±0.25% FS
Thin lm strain gauge
Thin lm pressure transducers are made by vapor deposition or sputtering
of insulation and strain gauge elements directly on a polished pressure
sensing diaphragm or beam. The desired strain gauge pattern is deposited
either by masking the non-conductive areas or by etching away unwanted
conductive material.
Through a sputtering process, a small circuit is created that contains on
it a Wheatstone-bridge resistance network. As pressure is applied to the
diaphragm and unbalances (or strains) the bridge, its electrical resistance
is changed and results in a voltage output.
1 to 15,000 PSI
G, C, S, V, A
75 to 32,000 PSI
G, C, S, A
Temperature
compensation
resistor
Wheatstone
bridge resistors
-40°C to 125°C
-40°C to 125°C
Excellent resistance to shock, vibration, and dynamic pressure changes
—
Measurement cell is hermetically sealed and does not
require additional sealing materials
—
Like variable capacitance technology, does not exhibit position effect
Advantage of
thin lm
strain gauge
sensors
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