How do I Check my Ultra Low Freezer for Temperature Accuracy?
Check your ULT Freezer for Temperature Accuracy: What Tools to Use?
The simplest way to check the temperature accuracy of your ultra low temperature freezer is to use a calibrated, NIST-traceable data logger or temperature probe. Place the probe inside the cabinet, ideally near the center where samples are stored. Check this temperature reading against the digital temperature display on your freezer.
It can also be helpful to check temperatures at multiple locations inside the cabinet including corners and overpacked sections. Make sure these areas are holding the temperatures you need. Ideally, you should identify critical areas in the freezer that fluctuate or “hot spots” and place probes in these areas. Hot spots tend to build in corners or across shelving or cramped sections of your freezer.
By monitoring these zones, you’ll be able to strategically store your samples and be aware of inaccuracies in your specific freezer. Reference our temperature monitoring blog to explore more ways to track temperatures in your ULT.
How Often Should you Track Temperatures in your ULT Freezer?
To determine the temperatures in your ULT most accurately, be sure to track temperatures continuously for at least 24-72 hours. Don’t open the freezer door within this time period. This length of time with no door openings will help you determine the baseline temperature of your freezer at rest.
You can also track temperatures with 30 second and 1 minute door openings. Use these metrics to see how temperatures fluctuate and how quickly your unit recovers back to setpoint. This can be helpful if you’re dealing with very delicate samples and need to make sure temperatures are kept within the correct range, even during door openings.
How Often Should you Professionally Calibrate your ULT Freezer?
It is highly recommended to have your ULT freezer professionally calibrated and validated by a qualified service technician at least once a year. These technicians use specialized, NIST-traceable calibrators (e.g., dry block calibrators capable of reaching -100°C) to ensure the accuracy of your freezer’s internal control and temperature probes.
Professional calibration can give you peace of mind knowing your samples are being stored at accurate temperatures and in safe conditions. By a simple professional calibration, you can save an enormous amount of research, time, money, and waste.
The Power of Maintenance to Maintain Temperatures in your ULT
Don’t underestimate the power of maintenance in maintaining ULT freezer temperature accuracy. Simple preventative measures such as cleaning condenser coils and checking door gaskets are crucial for the freezer’s best performance and temperature stability. Also, routine defrost cycles are key to a well-run freezer. Don’t underestimate the power of defrosting. A clean, well-maintained ULT means more efficient, accurate, and safe. Plus it will help keep your temperatures stable. Wins all around.
New to the world of ULTs? Explore our ULT freezer selection at ABS or reach out to our friendly customer service team at 1-843-821-8010 Option #3 or customerservice@horizonscientific.com.

Technical Writer and Marketing Editor
Christine works as a Technical Writer for Standex Scientific. She holds a B.A. in Creative Writing and has used her writing expertise in various companies from engineering firms to non-profits.