Chris Loiacono wrote...

>Dave, what temperature range have you tested your design in?

The product using the MPX4200A is specified for operation between -20C
and +70C, but the sensor itself is rated for -40C to +125C (Motorola
designed it for automotive use in turbocharger systems).  During
development, I tested from -80C to +130C with good results.

The product is an analog design that re-scales the MPX4200A output to a
different offset and span, and adds a second level of temperature
compensation for both offset and span shift to keep the final output to
within +/- 0.25% of span over the full temperature range.  I calibrate
the units to within 0.05% of span, giving some margin for aging, supply
variations, and so forth.  I've had no trouble doing this, which
indicates how well-behaved the basic sensor is.

The error behavior you're seeing in the MPX5700 is certainly odd, to say
the least; I've seen nothing like that on the MPX4200A- only a gradual
change in output scale factor over temperature, mostly at low
temperatures.  There appears to be almost no zero shift with
temperature, less than 10 millivolts.  Makes me wonder if the MPX5700
has some sort of design flaw.

Dave

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