20PC SMT Pressure Sensors
Common Mode Pressure (CMP)
Technical Note
Sensing and Control Copyright by Honeywell, June 2001
BACKGROUND
Honeywell Sensing and Control’s 20PC surface
mount transducer (SMT) products may be used in a
wide variety of applications and markets. To ensure
optimum performance, it is important to consider
the effects of common mode pressure when using
the 20PC SMT product in various applications.
PURPOSE
To assist our customers with the specifying
process, this technical note provides common mode
pressure information.
COMMON MODE PRESSURE
The 20PC SMT product has an output
proportional to CMP. This product’s output
responds very linearly and predictably to CMP.
Because pressure sensors are stress sensors, they
will respond to any kind of stress.
An increase in common mode pressure (psi)
generally makes the null shift offset (mV) become
more negative (see graph). This is due to a slightly
different seal durometer (hardness measurement)
value on one side of the sensing chip (piezoresistive
die) versus the other side. The biggest concern
with an output that varies with CMP is that it is
impossible to tell the difference between a change
in CMP and a change in pressure on one side of the
sensing chip versus the other side when measuring
differential pressure. If an application has a varying
CMP, you may eliminate this concern by installing a
second pressure gauge sensor to monitor the CMP.
This second sensor will allow you to measure a
change in CMP and compensate for its effect on the
null shift offset (see graph).
CONTACT INFORMATION
For additional assistance, call our application
center (1-800-537-6945) and speak to one of our
application engineers.
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CMP (psi) vs. NULL SHIFT (mV)
Common Mode Pressure (psi)
Null
Shift
mV