BMP581 temperature affecting pressure reading

[lucas_allen]

I am attemting to use the BMP581 to measure height change but it seems that changes in temperature of the sensor is having a massive effect on the pressure readings. 

I am using the sensor in the form of the sparkfun bmp581 breakout board and interfacing via I2C.

startup procedure:

reading device id at register 0x01 gives a value of 0x50

reading register 0x28  gives a value of 0x02

reading int status register 0x29 gives a value of 0x10

write register 0x36 with value of 0x60  to set press_en=1, osr_p=16x,   osr_t=1x

write register 0x37 with value of 0x5d  to set power_mode=normal,  odr=10hz

read procedure:

burst read six bytes starting at register 0x1d 

temperature =bytes[0-2]/65536

pressure=bytes[3-5]/64

here is a graph of temperature(bottom) vs pressure(top) over time when i placed my finger on the back of the breakout board to apply heat and then released to allow it to cool.

the bmp581 is supposed to have an absolute pressure accuracy of +-30pa

is my sensor faulty or am I doing something wrong?

any help would be greatly appreciated

[MrjT]

Hello Lucas,

It is likely that, in pressing your finger on the back of the board, you are inducing mechanical stress / deformation on the board which can corrupt the pressure measurement. 

Sections 7.1.2 to 7.1.10 of BMP5xy HSMI (bosch-sensortec.com) show some guidelines on avoiding mechanical stress on the sensors. We'd recommend using (gentle) warm air to heat the BMP581 to see if this reduces the pressure variations you are seeing.

[lucas_allen]

Hello MrjT,

Thank you for bringing this to my attention. I will definitly take this into consideration for my design, but I have confirmed that my sensor was faulty.

I just tested a new bmp581 sensor with the same code and the performance was impressive.

The sensor could reliably detect height changes of around 10cm and seemed to be compensating well for temperature changes.

[BSTRobin]

Hi lucas_allen,

As mentioned by MrjT, the BMP5xy HSMI document states the need to avoid mechanical stress and heat sources.
Additionally, if you still feel that your sensor is faulty, you can confirm it with your supplier. If you purchased the sensor from an official distributors or sales representatives , they will inspect it based on your stock.