Bosch Sensortec | BST-BMP581-DS004-11

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Document number: BST-BMP581-DS004-11

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4.4.2 Pressure and temperature oversampling ratio (OSR)

Oversampling extends the measurement time per measurement by the oversampling factor. Higher oversampling

factors offer decreased noise at the cost of higher power consumption.

Oversampling can be set individually for pressure and temperature in register fields OSR_CONFIG.osr_p and OSR_-

CONFIG.osr_t. The duration of the sampling phase, is given by tconv_p and tconv_t. Table 7: maximum nominal ODR

setting per OSR settings in NORMAL mode shows the maximum ODR for each oversampling setting. Recommended

settings are shown in Table 9: Oversampling settings .

Table 9: Oversampling settings

Oversampling setting

osr_p

Pressure

oversampling

Temperature

oversampling

Typical

pressure

RMS noise

at 100kPa

Typical ODR in

CONTINUOUS

mode

Lowest power

000

×1

×1

0.78 Pa

498 Hz

001

×2

×1

0.58 Pa

374 Hz

Standard resolution

010

×4

×1

0.41 Pa

255 Hz

011

×8

×1

0.30 Pa

155 Hz

High resolution

100

×16

×1

0.21 Pa

87 Hz

101

×32

×2

0.15 Pa

46 Hz

110

×64

×4

0.11 Pa

24 Hz

Highest resolution

111

×128

×8

0.08 Pa

12 Hz

Note: The noise values refer to the sensor-intrinsic noise. Already at standard resolution, the noise or fluctuations of

the air pressure itself may be higher than the noise of the sensor, and thus be dominant. This ambient noise is typically

stronger at lower frequencies. Any increase of the ODR does not reduce this type of noise, because this frequency

range is of interest for many applications and thus is not attenuated by the sensor. If low frequency noise is a problem

in a use case, it is recommended to employ low pass filtering, for example by using the build-in IIR-filter.

4.4.3 Configuration changes in NORMAL and CONTINUOUS mode

If any of these changes is applied during NORMAL and CONTINUOUS mode:



OSR_CONFIG.press_en



OSR_CONFIG.osr_t



OSR_CONFIG.osr_p



ODR_CONFIG.odr (NORMAL mode only)

Measurements will restart with the new settings after treconf. If DEEP_SLEEP is enabled in NORMAL mode, it will start

after treconf_deep.

4.4.4 IIR filter

The BMP581 has a dedicated IIR filter built-in, that can be used to reduce noise caused by ambient disturbances. This

may for example be the opening of doors or windows, or wind blowing into the sensor. To suppress these disturbances

in the output data, the IIR filter can be enabled.

Please note that IIR filtering, like all low pass filtering, also reduces the bandwidth of the signal.

The filter function is the following:

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