Book Image

Raspberry Pi Sensors

By : Rushi Gajjar
Book Image

Raspberry Pi Sensors

By: Rushi Gajjar

Overview of this book

Table of Contents (16 chapters)
Raspberry Pi Sensors
Credits
About the Author
Acknowledgements
About the Reviewers
www.PacktPub.com
Preface
Index

InsideDHT – temperature and humidity sensors


DHT is a combined pack of temperature and humidity sensors. These sensors are ideal for hobbyists who just want to do some data logging. DHT11 sensors are slow in terms of retrieving data. As it is a combined pack, it contains a resistive thermal sensor (a thermistor) and capacitive humidity sensor. A thermistor changes its resistance value depending on the changes in temperature. Technically, all resistors act as thermistors because they dissipate heat when the current is passed through them and are responsible for power losses. However, a resistor's characteristic is that when they are heated up from the external source, the resistance values changes a little bit, which is not so effective to be measured. But this is not the case with the thermistor; its resistance values change in terms of several hundred ohms when there is a slight change in the ambient temperature. A DHT11 temperature sensor provides accuracy near to 2 degree Celsius in the...