SX Series
Pressure sensors
4/10
July 2008 / 052
www.sensortechnics.com
MECHANICAL AND MOUNTING CONSIDERATIONS
PHYSICAL CONSTRUCTION
Button sensor element
The button sensor element was designed
to allow easy interface with additional
cases and housings which then allow
pressure connection. The device can be
mounted with an o-ring, gasket, or RTV
seals on one or both sides of the device.
The device can then be glued or clamped
into a variety of fixtures and the leads can
be bent as necessary to allow for ease of
electrical connection. However, caution is
advised as repeated bending of the leads
will cause eventual breakage.
For most gage applications, pressure
should be applied to the top side of the
device
(see
Physical
Construction
Drawing). For differential applications, the
top side of the device (P1) should be used
as the high pressure port and the bottom
(P2) as the low pressure port.
The button SX package has a very small
internal volume of 0.06 cubic centimeters
for P1 and 0.001 cubic centimeters for P2.
“N” packaged sensor
The "N” packaged sensor is designed for
convenient pressure connection and easy
PC board mounting. To mount the device
horizontally to a PC board, the leads can be
bent downward and the package attached
to the board using either tie wraps or
mounting
screws.
For
pressure
attachment, tygon or silicon tubing is
recommended.
The “N” package version of the sensor has
two (2) tubes available for pressure
connec-tion. For gage devices, pressure
should be applied to port P1. For differential
pressure applications, port P1 should be
used as the high pressure port and P2
should be used as the low pressure port.
GENERAL DISCUSSION
Output characteristics
The SX series devices give a voltage output
which is directly proportional to applied
pressure. The devices will give an increase
in positive going output when increasing
pressure is applied to pressure port P1 of
the device. If the devices are operated in
the backward gage mode, the output will
increase with decreases in pressure. The
devices are ratiometric to the supply
voltage. Changes in supply voltage will
cause proportional changes in the offset
voltage and full-scale span.
User calibration
SX series devices feature the button IC
pressure sensor element. This will keep
overall system costs down by allowing the
user to select calibration and temperature
compensation circuits which specifically
match individual application needs. In most
cases, the primary signal conditioning
elements to be added to the SX by the user
are: offset and span calibration and
temperature compensation.
Some typical circuits are shown in the
application section.
Vacuum
reference
(absolute
devices)
Absolute sensors have a hermetically
sealed vacuum reference chamber. The
offset voltage on these units is therefore
measured at vacuum, 0 psia. Since all
pressure is measured relative to a vacuum
reference, all changes in barometric
pressure or changes in altitude will cause
changes in the device output.
Media compatibility
SX devices are compatible with most non-
corrosive gases. Because the circuitry is
coated with a protective silicon gel, some
otherwise corrosive environments can be
compatible with the sensors. As shown in
the physical construction diagram below
for the button sensor element and ,,N”
package, fluids must generally be
compatible with silicon gel, RTV, plastic, and
aluminum for forward gage use and RTV,
silicon, glass and aluminum for backward
gage or differential applications. For
questions concerning media compatibility,
contact the factory.
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