BMP 280 accuracy

[szohar]

Hi,

We are using the BMP280 in a production design.

We messured few off them and we see in all an Absolute accuracy pressure errors of about 4hPa.

The registers are set as follow 

ctrl_meas 0B10110111 //Temp OS 16X, Press OS 16x, Power Normal

config 0B01010000 ////Inactive 125ms, IIR Filter coefx16, SPI OFF

The Temp I am getting is 32C.

I was using the compensation method given in the API example.

What can be the issues that cases those accuracy problems.

In the data sheet it is also mentioned that for better accuracy please contact the manufacturer, so I do.

Thanks

Sharon

[Jet]

Hi Sir:

     You still need to offer the raw data of termperature and pressure from sensor / the compensated pressure and temperature, I don't use my own sensor value to verify your trim values.

     Thank you.

[szohar]

Hi,

Please see below.

Your prompt help will be appricated. 

Uncompensated presure is 

Details:333767.375
Decimal:333767
Hex:0x517c7

Compensated presure is

Default:100180.547
Decimal:100180
Hex:0x18754

Uncompensate Temp

Default:516833
Decimal:516833
Hex:0x7e2e1

Compensate Temp

Details:2307
Default:2307
Decimal:2307
Hex:0x903

[Jet]

Hi Sir:

     I used your trim values and your raw data, but got the different value of the pressure.

    Please see the following log which is that used your trim values and your raw data:

    BMP280_CTRL_MEAS_ADDR =0xb7,BMP280_CONFIG_ADDR =0x50
BMP280 Shuttle Trim values
dev->calib_param.dig_t1 = 27766
dev->calib_param.dig_t2 = 26578
dev->calib_param.dig_t3 = -1000
dev->calib_param.dig_p1 = 36265
dev->calib_param.dig_p2 = -10611
dev->calib_param.dig_p3 = 3024
dev->calib_param.dig_p4 = 3504
dev->calib_param.dig_p5 = 214
dev->calib_param.dig_p6 = -7
dev->calib_param.dig_p7 = 15500
dev->calib_param.dig_p8 = -14600
dev->calib_param.dig_p9 = 6000
BMP280 Single CHIP Trim values
dev->calib_param.dig_t1 = 27680
dev->calib_param.dig_t2 = 26163
dev->calib_param.dig_t3 = 50
dev->calib_param.dig_p1 = 38057
dev->calib_param.dig_p2 = -10462
dev->calib_param.dig_p3 = 3024
dev->calib_param.dig_p4 = 6385
dev->calib_param.dig_p5 = -7
dev->calib_param.dig_p6 = -27
dev->calib_param.dig_p7 = 15500
dev->calib_param.dig_p8 = -14600
dev->calib_param.dig_p9 = 6000
Enter BMP280 Task Loop!
UT: 516833, T32: 2307, Double_T: 23.068108
UP: 333767, P32: 100248
UT: 51681UT: 516833, T32: 2307, Double_T: 23.068108
UP: 333767, P32: 100248
UT: 516833, T32: 2307, Double_T: 23.068108
UP: 333767, P32: 100248

Frow above log, you can get my trim values, my sensor raw data  and output results, please see the following log:

UT: 529941, T32: 2706, Double_T: 27.064492
UP: 400952, P32: 102207
UT: 529951, T32: 2707, Double_T: 27.067641
UP: 400949, P32: 102207

Compared with other sensors, these results are normal within the permitted range.

Please see the attachment, which is my source code.

[szohar]

Thanks for the information.

I will check to understand why there is a different in compensated presure but the different that you get is about 0.6hPa, we are getting diffrences of over 4hPa which is a major trouble for us.

Why the difference compared to reality can be so major out of spec dramaticaly?

Thanks

Sharon

[szohar]

Also looks as some of the variables you entered are switched as an example you can see that P2 and P3 are switched.