3 Ways Temperature Fluctuates in Fridge & Freezer Monitoring
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CLEVELAND - OhioPen -- Guide to Implementing Automated Refrigerator Temperature Monitoring

When installing new temperature monitoring systems in refrigerators and freezers, it's common to observe unexpected temperature fluctuations. Our advanced data loggers and monitoring systems offer faster response times and more comprehensive data than traditional thermometers, enabling better insight into temperature behavior. Use our guide to troubleshoot and improve temperature stability.

There are 3 common reasons the recorded temperatures can periodically change:

1. Frequent Door Opening

Unstable temperature readings in refrigerators/freezers are often caused by staff opening the door, leading to rapid changes in sensor-reported air temperature. However, actual product temperature remains stable. To address this issue, the CDC Vaccine Storage and Handling Toolkit recommends using a buffered thermal probe to dampen rapid temperature spikes.

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2. Refrigerator/Freezer Compressor Cycling

The second source of temperature variation arises from the normal cycling of the compressor used to cool the refrigerator/freezer. If comparing thermometer and electronic monitoring system readings, thermometer response time may hide actual fluctuations. A temperature vs. time graph shows regular temperature changes. Placing the monitoring system's probe near the evaporator coil or coil fan airstream isn't ideal. Relocating the probe can reduce the variation

3. Electrical Noise

The final cause is due to electrical noise in the monitoring system. This can often be identified from the temperature data in the form of random jumps in temperature from 0.5 to 5 degrees or more happening over a very short period (such as seconds). The most common cause of electrical noise is the placement of wires running from the sensor to the actual measurement instrument. The signal levels generated with some of the common types of sensors are often in the millivolt or microvolt range. If the wires carrying these signals pass near wires carrying AC line voltage power signals for motors or other devices, it's easy to get stray voltage induced on the temperature signal from the sensor. To fix this, make sure to carefully route wires from the temperature sensor away from any wires away from wires carrying AC power, use twisted pair wiring, and use shielded cable for the sensor wires, ensuring that the shielded cable is connected to good earth ground at just one end.

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Summary

Utilizing these suggestions with your fridge monitoring system, you should be able to minimize or remove the majority of temperature fluctuations in your medical refrigerator, perishable freezer, or any fridge/freezer/cooler unit you rely on to keep your product safe.

For more information on Fridge Monitoring Systems or to find the ideal solution for your application-specific needs, contact a CAS DataLogger Application Specialist at (800) 956-4437 or visit us at https://www.dataloggerinc.com.