Overview of the basic information and our tips for CO2, VOC, humidity, temperature, liquid and gas flow sensors. If you are looking for a solution, Sensirion will not disappoint you.
Sensirion sensors measure reliably all the important environmental parameters such as relative humidity, temperature, the concentration of CO2, VOC and concentration of particulate matter. Sensirion also offers sensors for measuring liquid flow and the gas mass flow.
The Basics
Sensors are based on measuring the capacitance between electrodes placed in a porous polymer membrane. Water vapor penetrates into the membrane and changes the capacitance between electrodes.
You can find the sensor comparison in the table below.
The table is available in PDF format.
STSx Sensors
The STS21 temperature sensor has the same parameters as SHT21 except for lower average current consumption 20uA because of T_meas=66ms instead of T_meas+RH_meas=66ms+22ms for SHT21. The sts3x temperature has the same parameters as SHT3x but they measure only temperature.
Sensors Lifecycle
SHT1x sensors are not manufactured anymore. You can, therefore, use SHT3x sensors. Migration requires PCB redesign because of the different package and SW changes since SHT3x uses I2C interface instead of S-bus.
SHT7x sensors were also discontinued. Please, use SHT85 instead. Migration requires SW changes because SHT85 uses I2C interface.
SHT2x and SHTC1 are in mass production. Even though there isn’t a plan to stop the production, we recommend using the SHT3x and SHTC3 for the new projects.
SHTW1 sensor is not manufactured anymore, please use SHTW2 (different package, PCB redesign is necessary).
Battery operation
Lithium (Lithium-thionyl Chloride) battery has a nominal voltage 3V (3.6V). The battery is fully depleted when the voltage drops to 2V (cut-off voltage). All RH&T and T sensors have low current consumption and can work from a battery, but:
● SHT3X works in range 2.15 to 5.5V – can’t make use of full battery capacity
● SHTC1, SHTW2 works in range 1.62 to 1.98 – they need voltage regulator and I2C level shifter
● SHTC3 works in range 1.62 to 3.6V – covers full battery voltage range
