XDK API  3.6.0
EnvironmentalUtils.h File Reference

Environmental Sensor Utilities. More...

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Retcode_T SetAmbientTemperatureOffset (float T_offset)
 Register the ambient temperature offset in degree C. More...
float GetAmbientTemperatureOffset (void)
 Returns the ambient temperature offset. More...
float ComputeAmbientTemperature (float T_sensor)
 Compute Ambient Temperature. More...
float ComputeAmbientHumidity (float rH_sensor, float T_sensor, float T_ambient)
 Compute Ambient Humidity. More...

Detailed Description

Environmental Sensor Utilities

The environmental sensor utilities consists of APIs that aid in compensating effects due to self-heating of the XDK during normal conditions

As any electronic component, the sensor is subject to self-heating, which can be from the sensor itself, as well as from other components used at the time of measurement.

Unfortunately, this self-heating strongly depends on the usage, and as the XDK can be freely programmed, we cannot provide a universal compensation algorithm.

The accuracy of the humidity measurement is strongly related the temperature; as relative humidity is calculated using the temperature reading.

Hence, a higher temperature leads to a lower relative humidity.

Once the temperature compensation is done, the relative humidity can be calculated using the temperature difference.

Function Documentation

float ComputeAmbientHumidity ( float  rH_sensor,
float  T_sensor,
float  T_ambient 

Computes the ambient relative humidity using the Tetens formula for estimation of ambient vapor pressure

Compensation formula:

Rh_ambient = Ew(T_sensor) / Ew(T_ambient) * Rh_sensor

The vapor pressure of water approximation used is the Tetens formula with a validity range between -10 degree C and 75 degree C
Sensor values are measured inside the device housing
This function has a division by zero in the case where T_sensor or T_ambient is equal to -TETENS_BETA_NEGATIVE (-265.5 degree C)
[in]rH_sensorRelative humidity measured by the sensor
[in]T_sensorTemperature in degree C measured by the sensor
[in]T_ambientTemperature in degree C measured or estimated outside
rH_ambient Computed ambient relative humidity

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float ComputeAmbientTemperature ( float  T_sensor)

Ambient Temperature is calculated by adding an offset to the measured sensor temperature

Compensation formula:

T_offset = T_ambient - T_sensor

T_ambient = T_sensor + T_offset

This API provides a default value for the temperature offset value.
[in]T_sensorTemperature in \C measured inside
T_ambient Calculated ambient temperature

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float GetAmbientTemperatureOffset ( void  )
Ambient Temperature Offset
Retcode_T SetAmbientTemperatureOffset ( float  T_offset)
returnCode Return code indicating state and success of the operation
Return values
RETCODE_OKoperation was successful
RETCODE_INVALID_PARAMInvalid Temperature offset

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All rights reserved. The use is subject to the XDK SDK EULA by Bosch Connected Devices and Solutions GmbH.
This documentation file has been automatically generated on Thu Mar 14 2019 19:12:48 by doxygen 1.8.8