Module/Sensirion SHT25
Overview
The Sensirion SHT25 is a digital temperature and relative humidity sensor. Adaption speed is not perfect.
| Module name | meteo/humid_sht_i2c |
| Sensor type | humidity, temperature |
| Range (humidity) | 0 .. 100 %RH |
| Range (temperature) | -40°C .. +125°C |
| Resolution (humidity) | 0.04 %RH |
| Resolution (temperature) | 0.01°C |
| Refresh rate | 4Hz |
Hardware
The sensor is supplied with an I2C interface. There will be an adapter board available in the Paparazzi hardware repository.
Supplier:
Wiring
| Autopilot I2C pin | Autopilot I2C | SHT25 | SHT25 pin |
| 1 | GND | GND | 1 |
| 2 | |||
| 3 | +3.3V | Vcc | 4 |
| 4 | SDA | SDA | 2 |
| 5 | SCL | SCL | 3 |
Usage
To use the humidity sensor add:
| File: conf/airframes/myplane.xml |
<modules>
<load name="humid_sht_i2c.xml"/>
</modules>
|
Result message
The raw data (ihumid/itemp) and the converted result (humid/temp) is written to the log file. The message is automatically sent when new data is received, it does not have to be added to the telemetry file.
| File: conf/messages.xml |
<message name="SHT_I2C_STATUS" id="127">
<field name="ihumid" type="uint16"/>
<field name="itemp" type="uint16"/>
<field name="humid" type="float" unit="rel_hum" format="%.2f"/>
<field name="temp" type="float" unit="deg_celsius" format="%.2f"/>
</message>
|
The sensors 64bit serial number is read out at init and transmitted every 30 seconds.
| File: conf/messages.xml |
<message name="SHT_I2C_SERIAL" id="99">
<field name="serial0" type="uint32"/>
<field name="serial1" type="uint32"/>
</message>
|
Sample log file lines
4.000 123 SHT_I2C_SERIAL 8388707 -1365769984 4.393 123 SHT_I2C_STATUS 36668 26928 63.93 25.35 4.645 123 SHT_I2C_STATUS 36648 26924 63.9 25.34 4.893 123 SHT_I2C_STATUS 36660 26924 63.92 25.34
NOTES
The location of the sensor on the aircraft does matter. There are various papers that analyze the best location. So far we have installed them within tubes (to protect from sunlight/heating) on the wings. That might not be the optimum place. The SHT25 is not preferred as it does have holes on the back that allows the air to flow through.