durusmail: mems-talk: Low-pressure Sensor
Low-pressure Sensor
2005-02-11
2005-02-11
Low-pressure Sensor
Rich Rosenblum
2005-02-11
Jay.

 How low in pressure do you need to go?    I was also not clear from your
question if you are concerned with zero changes as the temperature is
changed or if you are concerned about permanent changes once you go to a
temperature extreme and return to normal.

Many sensor packages have built in compensation for temperature changes.
There are two types.  One type is analog correction and the other is
digital.   The idea is to first characterize the zero changes (and span
for that matter) at the needed temperatures.  From this data, correcting
algorithms or analog circuitry can reconstitute the correct readings.

To guard against permanent changes,  the type of silicon die,  constraint
and mounting arrangement  are key controlling factors.   Another
requirement  is keeping the temperature swings within the specified
temperature band of operation.

By combining accurate compensation and proper mounting, one can even take
a 1 psig sensor below that level and still get a relatively stable sensor.
 If you need to go extremely lower than 1 psig, then some type of periodic
calibration may be required.

Checkout www.sensorsmag.com for a listing of sensor companies.  On the
left tab, under Problem Solvers, Click Buyers Guide.   Ametek makes
sensors with standard ranges as low as 1 psi.

Rich Rosenblum
Principal Electrical Engineer
Ametek USG, PMT Products
215-354-1826
rich.rosenblum@ametek.com

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