ILPS28QSW datasheet(13/52 Pages) STMICROELECTRONICS

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5.5

Interpreting pressure readings

The pressure data are stored in three registers: PRESS_OUT_H (2Ah), PRESS_OUT_L (29h), and

PRESS_OUT_XL (28h). The value is expressed as a 24-bit signed number (in two's complement).

To obtain the pressure in hPa, take the complete 24-bit word and then divide by the sensitivity 4096 LSB/hPa

when the FS_MODE bit is 0 (in mode 1, full scale is up to 1260 hPa) or divide by the sensitivity 2096

LSB/hPa when the FS_MODE bit is 1 (in mode 2, full scale is up to 4060 hPa). This same interpretation

is applied to pressure readings when FIFO is enabled and the pressure data are stored in three registers:

FIFO_DATA_OUT_PRESS_XL (78h), FIFO_DATA_OUT_PRESS_L (79h), and FIFO_DATA_OUT_PRESS_H

(7Ah).

Figure 6. Pressure readings

PressureValue=PRESS_OUT_H2Aℎ &PRESS_OUT_L29ℎ &PRESS_OUT_XL

28ℎ =3FF58Dℎ=4191629LSB signeddecimal

(1)

(2)

When the FS_MODE bit = 0, (CTRL_REG2 (11h)) for full scale up to 1260 hPa:

Pressure ℎPA =Pressurevalue LSB

Sensitivity = 4191629LSB

4096LSB/ℎPA=1023.3ℎPA

When the FS_MODE bit = 1, (CTRL_REG2 (11h)) for full scale up to 4060 hPa:

Pressure ℎPA =Pressurevalue LSB

Sensitivity = 4191629LSB

2048LSB/ℎPA=2046.7ℎPA

5.6

Interpreting temperature readings

The temperature data are stored in two registers: TEMP_OUT_H (2Ch) and TEMP_OUT_L (2Bh).

The value is expressed as two's complement. To obtain the temperature in °C, take the two’s complement of the

complete 16-bit word and then divide by the sensitivity 100 LSB/°C.

Figure 7. Temperature readings

0 0 0 0 1 0 0 1

1 1 0 0 0 1 0 0

TEMP_OUT_H

TEMP_OUT_L

Temperature Value (LSB) = TEMP_OUT_H (2Ch) & TEMP_OUT_L (2Bh)

= 09C4 = 2500 LSB (decimal signed)

Temperature (°C) =

Temperature Value (LSB)

Sensitivity

2500 LSB

100 LSB/°C

= 25.00°C

ILPS28QSW

Interpreting pressure readings

DS13905 - Rev 1

page 13/52

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