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How to Calibrate Wireless Temperature Sensors

Out of the box, ALTA Wireless Standard Temperature Sensors are accurate to +/- 1% (1° C or 1.8° F), and calibration provides even greater accuracy of +/- 0.25° C (± 0.45° F). If you aim to achieve greater accuracy or believe the reading for a Temperature Sensor is inaccurate, you can calibrate or set default calibration in Iotplus. Executing a successful calibration includes some important considerations.

Things to consider


Important Calibration saved to the portal is not applied until the sensor’s subsequent communication. Therefore it’s important to leave the sensor probe at a stabilized temperature until the next Heartbeat after the calibration is saved in Iotplus. Until the calibration is applied to the sensor, you will see the message, “Fields waiting to be written to sensor are not available for edit until transaction is complete.” You’ll also see the icon shown below.
Pending Configuration


Although it’s possible to calibrate using the default 2-hour Heartbeat, you may consider setting the Heartbeat of both the gateway and the sensor to the most frequent Heartbeat allowed on your network. This may be advisable to accommodate the time difference between 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 in smaller time increments. We recommend you calibrate your sensor in an environment with a stable, uniform temperature. If you see temperature fluctuations, you may be unable to execute a successful calibration.


You should always wait long enough for exposed sensor parts 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. Typically, 90 minutes of stable readings will generally yield the desired result. Often the most significant 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.


The calibration function is a linear calibration, so we recommended that you calibrate the sensor in the temperature range that it will be monitoring. You may find that if you calibrate at room temperature and then place the sensor in a refrigerator or freezer, the calibration may be off. Also note, elevation and other environmental factors can affect your calibration results.


The physical condition of your sensor can also influence calibration. Ensure your sensor (especially the probe) is free of dust, oil, paint, and any other material influencing accuracy.

Access the Temperature Sensor’s Calibrate Tab

If your sensor supports calibration, there will be a tab labeled Calibrate visible when viewing the sensor through the Iotplus Online Portal. To view the sensor’s calibrate tab:

Set the calibration to default

Before calibrating, you may want to reset the calibration to default if the sensor was previously calibrated.

Enter and save the calibration value

Important Be sure to leave the sensor probe in the calibration environment until the calibration has been applied to the sensor on its Heartbeat subsequent to clicking the Calibrate button.

  • Select the sensor you want to calibrate.
  • Select the Calibrate tab.
  • Enter the observed temperature (this is the temperature you are expecting the sensor to report) in the “Actual reading is” field; be sure to enter in Fahrenheit or Celsius corresponding to the configured Scale for that sensor.
  • Click the Calibrate button.
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  • Leave the sensor in the stabilized temperature until the calibration is saved to the sensor.
  • The calibration will be applied on the sensor’s subsequent Heartbeat.
Calibrate using the ice bath method (leaded temperature sensors):
  • Combine water with a good number of ice cubes in an adequately sized container; allow 15 minutes or so for the water to become a uniform temperature and stir.
  • 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 (adjust for altitude).
  • As permitted, observe stabilization of readings for 90 minutes.
  • Enter the observed reading value to 0 °C (32 °F) or the freezing temperature of water for your altitude as per the steps above in the “Actual reading is” field.
  • Select the Calibrate button.
  • Calibration should be accepted on the subsequent Heartbeat.

After calibration

We suggest leaving your sensor at the stable temperature to observe the readings following the calibration and confirm success.

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