Calibrating Wireless Temperature Sensors

Out of the box, Monnit wireless temperature sensors are accurate to +/- 1°C (1.8°F) and calibration to the sensor’s working environment provides even greater accuracy. If you aim to achieve greater accuracy or believe the reading for your temperature sensor is inaccurate, you can calibrate or set default calibration through the iMonnit Online Portal. Since temperature often fluctuates over time, executing a successful calibration includes some important considerations.

Things to consider

Heartbeat

Although it is possible to calibrate using the default 2 hour heartbeat, Monnit recommends setting the heartbeat of both the gateway and the sensor to the most frequent heartbeat allowed on your network in order to account for the time difference between the user entering the calibration value and the sensor accepting the entered calibration. Also, configuring your sensor to a more frequent Heartbeat allows you to identify temperature fluctuations. Calibrating your sensor successfully will require the calibration to be executed in an environment with a stable uniform temperature. If you see temperature fluctuations, you may be unable to execute a successful calibration.

Stabilization

You should always wait long enough for exposed parts of the sensor to stabilize to the target temperature. When you expose a sensor probe to a specific temperature, it will always take some time before the temperature of the sensor hardware reaches the temperature of the environment and stabilizes. 90 minutes of stable readings will generally yield the desired result. Often the biggest factors leading to unsuccessful calibration results relate to calibration executed too quickly. Calibrating without a stable temperature is the most common factor that leads to an unsuccessful calibration.

Environment

The calibration function is a linear calibration so it is recommended that you calibrate the sensor in the environment that it will be measuring. It is not advised to calibrate a temperature sensor to room temperature and then place the sensor in a cooler or freezer. Elevation and other environmental factors can also affect your results and should be considered.

Condition

The physical condition of your sensor can influence calibration. Make sure your sensor is free of dust, oil, paint and any other material that can influence the accuracy.

Setting the calibration to default

Calibration Tab

• Click on the sensor you want to calibrate.
• Click on the calibrate tab.
• Click on Default to set the calibration to default.

If you believe you have an accurate reference and you prefer to calibrate your Monnit sensors accordingly, you can enter the value in the blank and click calibrate. The calibration will take place once the sensor checks in subsequently multiple times.

Ice Bath Method:

  1. Take a container of water and combine that with some ice cubes.
  2. Insert the lead into the ice bath (preferably a stirred one). The reading should be close to 0 °C (32 °F), though this can vary depending on altitude
  3. You can follow the steps above to set the calibration to 0 °C (32 °F) or the freezing temperature of water for your altitude

After Calibration

It is suggested you leave your sensor in the the stable temperature to observe the readings following the calibration to confirm it was applied successfully.