We are using a MPXHZ6115A6U to get an estimate of altitude by using the air presure. Our sensor is giving wild values on the analog port on some of our sensors

[daniel-morley]

We are using a MPXHZ6115A6U to get an estimate of altitude by using the air presure.  Our sensor is giving wild values on the analog port on some of our sensors.   Also increasing temperature changes these numbers significantly verses a functional part.   It is clear that a number of our parts are not working correctly giving us a value far under what the pressure should be.    Some thing we are doing is impacting the sensors and not the rest of the components around the part.  

[reyes]

Hi,

I believe that the error on the measurement you are seen could be caused by a drift/offset on the output signal, the sources of offset errors like this are due to device to device offset variation (trim errors), mechanical stresses (mounting stresses), shifts due to temperature and aging.

My recommendation is to implement the auto zero function, which can be easily implemented when using an integrated pressure sensor with a microcontroller. Auto-zero is a compensation technique based on sampling the offset of the sensor at reference pressure in order to correct the sensor output for long-term offset drift or variation.

The Application note AN1636 is a guideline for implement the Auto Zero function for Integrated Pressure Sensors to achieve higher accuracy: https://www.nxp.com/docs/en/application-note/AN1636.pdf

BTW, if you application require to measure altitude, I would rather recommend you to use the MPL3115A2 pressure sensor which is a digital altimeter and can give the output in meters by using an simple formula (section 9.1.3 of the MPL3115A2 datasheet: https://www.nxp.com/docs/en/data-sheet/MPL3115A2.pdf)

Regards,

Jose

NXP Semiconductor