The HDC1050 from Texas Instruments is a tiny 3 mm square combined humidity and temperature sensor. It can operate from a supply rail of 3 to 5 V and offers an accuracy of ±3 % on relative humidity measurement and ±0.2 ºC on temperature measurements. The typical supply current is 1.2 µA while operating at one sample per second and 100 nA in sleep mode.

Communication with the chip is via an I2C interface. After power up the device enters sleep mode and waits for an I2C command to configure the chip. Measurement resolution can be set to 8, 11 or 14-bit for humidity and 11 or 14-bit for temperature measurement. Conversion times can be up to 6.5 ms depending on the selected resolution. The chip also monitors the battery supply voltage. When a command is received to trigger a measurement, the HDC1050 wakes from sleep mode for measurement then returns back to sleep mode. The low power dissipation help minimize inaccuracies produced by self-heating.

The HDC1050 is priced at $2.88 per unit in quantities of 1000 units.