Temperature Sensor Accuracy, Alerts, and Reading Differences

Questions about temperature sensors that appear inaccurate or generate frequent temperature alerts are common. In most cases, the sensor is operating correctly, and the concern is related to differences between air temperature measurements, appliance displays, sensor placement, or alert configuration.

Monnit temperature sensors are designed to be highly accurate and responsive to environmental changes. Because of this, they may detect temperature fluctuations that other devices do not display or record.

Why Monnit Readings May Differ from Refrigerator or Freezer Displays

Concerns regarding sensor readings to the reading displayed on a refrigerator, freezer, incubator, or other equipment are common. Differences between these readings do not generally indicate a problem with the Monnit sensor.

Reasons for differing temperatures include:

• Built-in appliance displays may use sensors located in a different area than the Monnit sensor.
• Appliance displays often average readings over time, while Monnit sensors report actual measured temperatures at the time the reading occurred.
• Monnit sensors respond quickly to environmental changes such as door openings, product movement, airflow changes, and defrost cycles.
• Temperature can vary significantly within different areas of the same enclosure.

For these reasons, the Monnit sensor may report temperatures that differ from an appliance display while still operating accurately.

Confirming Sensor Accuracy

If sensor accuracy is a concern, one of the most effective tests is to compare the sensor against another Monnit temperature sensor in the same location.

Recommended Test

1. Place two Monnit temperature (or other types of) sensors side by side.
2. Reset the calibration to the default calibation using the blue Default button under the Calibrate tab (available on sensors that support calibration).
3. Configure both sensors to have the same Heartbeat if they do not already.
4. Power both sensors off for 60 seconds.
5. Power both sensors on at the same time.
6. Allow sufficient time for both sensors to stabilize - 90 minutes is recommended.
7. Confirm the probes are in the same locations (within an inch or so) or connected to the same source.
8. Compare the reported temperatures after 90 minutes (an during the stabilization).

If both sensors report similar readings, this strongly indicates that the sensors are functioning correctly and accurately measuring the environment.

Calibration Considerations

Monnit sensors are factory-calibrated prior to shipment.

If the sensor was not purchased with NIST certification, calibration adjustments should only be made under carefully controlled conditions using a trusted reference standard.

Improper calibration can introduce error rather than improve accuracy.

If calibration settings have been modified and accuracy is now in question, restore the factory settings by:

1. Opening the sensor settings page.
2. Navigating to the Calibrate tab.
3. Selecting Default to return to the original calibration values.

Sensor Placement Best Practices

Probe and sensor location can have a significant impact on reported temperatures.

When reviewing temperature concerns, verify that the sensor is not located:

• Near a door or frequently opened access point.
• In direct airflow from cooling equipment.
• Near an evaporator coil.
• Near a heater or warming element.
• Adjacent to a defrosting unit.
• In a location that does not represent the temperature of the monitored product.

Even a small change in placement can significantly affect readings.

Understanding Defrost Cycles

Many refrigeration systems periodically enter a defrost cycle. During these cycles, temperatures can temporarily rise above normal operating ranges.

Because Monnit sensors respond quickly to temperature changes, they may:

• Detect the temperature increase before it becomes visible on the appliance display.
• Trigger alerts during normal equipment operation.
• Show short-duration spikes in sensor history data.

If recurring alerts coincide with regular defrost cycles, the sensor may be functioning exactly as intended.

Using Temperature Buffers

For customers monitoring refrigerators, freezers, vaccines, pharmaceuticals, food products, or other temperature-sensitive materials, a temperature buffer may help produce readings that more closely represent the temperature of the stored product rather than the surrounding air.

Benefits of temperature buffers include:

• Reduced impact from brief door openings.
• Less sensitivity to short-term airflow changes.
• More stable temperature readings.
• Reduced nuisance alerts.

See Wireless Sensor Temperature Buffers for Consistent Readings for additional information.

Reducing Excessive Temperature Alerts

If alerts are occurring too frequently, consider adjusting notification settings instead of assuming a sensor issue exists.

Options include:

• Increasing notification delays.
• Requiring a condition to persist before generating an alert.
• Adjusting thresholds when appropriate.
• Reviewing alert settings around known defrost cycles.

These changes can reduce unnecessary notifications while still ensuring meaningful temperature excursions are reported.

Conclusion

In most cases, temperature differences between a Monnit sensor and another reference source are caused by sensor placement, environmental conditions, appliance display behavior, or the sensor's fast response time, rather than a sensor malfunction.

Before concluding that a sensor is inaccurate, Monnit recommends:

1. Comparing the sensor against another Monnit sensor.
2. Reviewing calibration settings.
3. Confirming proper sensor placement.
4. Considering a temperature buffer.
5. Evaluating notification delay settings and potential defrost-cycle impacts.

Following these steps will resolve the majority of perceived temperature accuracy concerns and help ensure confidence in the sensor's operation.