This page explains the JEMRF Wireless Temperature and Humidity Sensor

Product Description

Wireless temperature and humidity sensor with high degree of accuracy (~0.3°C and +-2% Humidity). Very low power and can last 6 months on a single CR2032 coin cell battery when configured to send readings every 10 minutes.


Install battery and close enclosure as described here.

Sensor testing

Product Specifications

Sensor (SHT21) Performance:

Wireless Sensor Graphs


  • 2.2-3.3V
  • Powered by CR2032 coin cell battery
  • Can be externally powered by soldering to the 3V3 and GND through holes on the PCB


  • Standard JemRF wireless sensor, refer RF Communications section for all the details
  • Highly configurable
  • If the RF module cannot find the BME280 sensor then it will report back (NOSENSOR). Check the wiring and power to the BME280 module.

Messaging details

  • TMPA99.99 (temperature reading format)
  • HUM99.99 (temperature reading format)
  • HTU21 (the SHT21 command requests the sensor to transmit a temperature and humidity reading)


  • 51mm x 36mm x 20mm case size (2” x 1.42” x .79”)

Default configuration

  • Type 10 (Type 10 sensor)
  • NOMSG2 (Sends 2 temperature & humidity readings every cycle)
  • INTVL005 (Sends a temperature reading every 5 minutes)
  • CYCLE (put the device into a timed sleep cycle)
  • Refer device configuration for more details