Datasheet

BMP280 Digital Pressure Sensor

Page 13

BST-BMP280-DS001-19 | Revision 1.19 | January 2018

Bosch Sensortec

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Note: Specifications within this document are subject to change without notice. Not intended for publication.

3.3.2 Temperature measurement

Temperature measurement can be enabled or skipped. Skipping the measurement could be

useful to measure pressure extremely rapidly. When enabled, several oversampling options exist.

Each oversampling step reduces noise and increases the output resolution by one bit, which is

stored in the XLSB data register 0xFC. Enabling/disabling the temperature measurement and

oversampling setting are selected through the osrs_t[2:0] bits in control register 0xF4.

Table 5: osrs_t settings

osrs_t[2:0]

Temperature oversampling

Typical temperature

resolution

000

Skipped

(output set to 0x80000)

–

001

×1

16 bit / 0.0050 °C

010

×2

17 bit / 0.0025 °C

011

×4

18 bit / 0.0012 °C

100

×8

19 bit / 0.0006 °C

101, 110, 111

×16

20 bit / 0.0003 °C

It is recommended to base the value of osrs_t on the selected value of osrs_p as per Table 4.

Temperature oversampling above ×2 is possible, but will not significantly improve the accuracy

of the pressure output any further. The reason for this is that the noise of the compensated

pressure value depends more on the raw pressure than on the raw temperature noise. Following

the recommended setting will result in an optimal noise-to-power ratio.

3.3.3 IIR filter

The environmental pressure is subject to many short-term changes, caused e.g. by slamming of

a door or window, or wind blowing into the sensor. To suppress these disturbances in the output

data without causing additional interface traffic and processor work load, the BMP280 features

next measurement step is filter using the following formula:

t

coefficien

filter

ADC

data

t

coefficien

filter

old

filtered

data

filtered

data

_

_

)

1

_

(

_

_

_









,

where data_filtered_old is the data coming from the previous acquisition, and data_ADC is the

data coming from the ADC before IIR filtering.

The IIR filter can be configured using the filter[2:0] bits in control register 0xF5 with the following

options:

rate of the sensor. E.g. environmental fluctuations caused by windows being opened and closed might have a frequency <5 Hz.

Consequently, a sampling rate of ODR = 10 Hz is sufficient to obey the Nyquist theorem.