Description
Humidity Sensor With Waterproof Connector
This humidity and temperature sensor is designed for wet and dirty environments. The I2C sensor is overmolded into a plastic housing which in turn plugs into a waterproof connector. This rugged sensor is suitable for a wide range of applications, from everyday settings like pools, aquariums, and agricultural setups to extreme environments such on the ski hill in snow making equipment.
This design is the result of feedback from a decade of experience providing humidity sensing solutions to OEMS tackling the most demanding of applications. The sensor is an OEM solution, it will require an interface to your CPU using the I2C protocol.
If the sensor should have problems you can quickly swap the module out with a new one using no tools, just pull the sensor off and plug in a new one.
The sensor is very small making it easy to mount in typical OEM tight spots like ducts and various nooks of OEM equipment.
There is a sintered stainless steel filter covering the sensor which provides an extra level of protection against splashes and dust yet allows vapor to pass to the sensing element.
4th Gen. High-Accuracy, Ultra-Low-Power, 16-bit, Relative Humidity and Temperature Sensor from Sensirion, SHT40 series sensing element.
Use this sensor with any CPU, see our  Humidity & temp transmitters for the typical electronics required to turn the I2C sensor into a 0-10V signal or communicate over RS485.
I2C Quick Start – Hello World
A typical application circuit for SHT40 is shown on the left-hand side of Figure 1. After reaching the minimal supply voltage and allowing for the maximal power-up time of 1 ms the sensor is ready for I2C communication. The quickest way to measure humidity and temperature is pseudo-coded on the right-hand side of Figure 1. Together with the conversion formulae given in equations ( 1 ), ( 2 ), and ( 3 ), the digital signals can be translated into relative humidity and temperature readings.
Pseudo code
i2c_write(i2c_addr=0x44, tx_bytes=[0xFD])
wait_seconds(0.01)
rx_bytes = i2c_read(i2c_addr=0x44,
number_of_bytes=6)
t_ticks = rx_bytes[0] * 256 + rx_bytes[1]
checksum_t = rx_bytes[2]
rh_ticks = rx_bytes[3] * 256 + rx_bytes[4]
checksum_rh = rx_bytes[5]
t_degC = -45 + 175 * t_ticks/65535
rh_pRH = -6 + 125 * rh_ticks/65535
if (rh_pRH > 100):
rh_pRH = 100
if (rh_pRH < 0):
rh_pRH = 0
See more detailed info on the Sensirion SHT40 series sensor element here: Sensirion SHT40
