This article is going a little bit technical so we will go straight forward to the points.
USB temperature logger is proved to be the most popular option in recording transit temperature in most logistic applications.
The design is quite simple with this product, but the details behind it are never that simple.
Key factor 1: Real traceability
All loggers collect temperature, with 2 options: an “internal NTC” or a “digital sensor”.
NTC is a much cheap option with lower support requirements from the system. While digital sensor is more expensive and requires more resource support internally.
When the NTC option is claimed to be NIST traceable, it means it has calibrated by a 3-point NIST calibration process, which shall take at least 2 hours each. You are not expecting the manufacturer do this for you on every single piece.
Digital sensor is pre-calibrated to NIST from its manufacturer, it however request more stable system support especially in low temperature low votage conditions.
Cydiance use digital sensors in all loggers, including USB/Bluetooth and realtime, no exception.
Key factor 2: Low temperature performance
Make sure you get a logger that can work to -30 Celsius if you are shipping something frozen.
You may well say your frozen shipment is only setting to -18 Celsius, however, it may experience temperature lower than -26 Celsius during working period of refrigerator, especially when problem happens, it goes down to even lower. And surely when problem happens, we are in desperate for these records.
We were having a test during the past months, with loggers from various manufacturers. Test was carried on with temperature range from -20 to -30 Celsius degrees, which is the claimed working temperature for all of them; the result suprisingly shows 80% of them failed. We are not going to name any to avoid misunderstanding but, you would have to pay attention to this.
Key factor 3: Failure proof strategy
All electronic device will make mistakes, therefor a “failure proof strategy” has to be deployed internally. For example, anti-static proof, compatibility, low voltage, non-stable connection etc.
USB temperature logger should be prepared for all these unexpected coincidences, and make sure integrity of content is kept. A good logger would be confident to work with an old computer with non-stable voltage usb port, and perform as normal.
This is a factor quite difficult to be proved especially when you are only using several units, but when failure happens, it will cause you huge problem and loss with your load.
We have a very complex system on this simple product, both hardware and firmware, to ensure it fix itself when something happens. And just recently we notice the importance of this, as we are having a lot of new clients now coming to us with this kind of bad experience.
We can continue with a lot more to share, but we believe these above should be the most important factors to consider before you make your decisions.
Recording temperature is easy, providing complete and reliable data is never easy.