SMD500 Datasheet, PDF (4/10 Pages) List of Unclassifed Manufacturers – Altimeter / Barometer Module ultra low power, low voltage

3. Measurement of pressure and temperature
The steps to measure pressure and temperature data and calculation of the physical values are shown in the following figures.
For all calculations presented here an ANSI C code is available.
To start a pressure or temperature measurement the microcontroller sends a start sequence. After the conversion time the result
value (UT or UP) can be read via the I²C interface. For calculating the temperature in °C and pressure in hPa the calibration data
is used. These constants can be read out from the SMD500 PROM once at software start-up.
The sampling rate can be increased up to 14 samples per second for dynamic measurement or to average out noise. In this case,
it is sufficient to measure the temperature only once per second and use this value for all pressure measurements in this period.
Using oversampling and averaging, the optimum compromise between power consumption, speed and resolution can be
selected, see table 1.
Table 1: Relation between averaging, power consumption, speed and resolution (at sea level).
mode
standard
high
resolution
high speed
pressure
measurements
per sec
1
number of
averages
1
temperature
measurements
per sec
1
data refresh
rate [Hz]
1
4
4
1
1
10
1
1
10
avg. current
consumption
[µA]
5
10
25
RMS noise
[hPa]
0.06
0.03
0.06
RMS noise
[m]
0.5
0.25
0.5
Start
start temperature
measurement
wait 34 ms
read UT
start pressure
measurement
wait 34 ms
read UP
Repeat if averaging is
requested
calculate pressure and
temperature in physical
units
Figure 2: Flow chart temperature and pressure measurement
4
Bosch Sensortec GmbH reserves all rights in the event of industrial property rights. We reserve all rights of disposal such as copying and passing on to third parties.
BOSCH and the symbols are registered trademarks of Robert Bosch GmbH, Germany.