How often should you calibrate your loggers, and how long does your certificate is valid for?

?The calibration interval should be defined by the client. Always. This is valid for your temperature loggers, but also for any other measuring device that could deviate over time.

You should detail a calibration interval in your SOPs. And this is for all your types of measuring devices.?

The vast majority of our clients require a new certificate every year. However, some organizations I have been working with, used to require a 6-month calibration. On the other end, some others ask to have their loggers calibrated every 2 years.?

So what should you do??

I recommend a calibration every year. If the majority of regulations and standards mention a “defined interval”, some are more specific (such as the World Health Organisation) and ask for “once a year” calibration.

The rationale to lengthen the calibration interval over 1 year should be based on stability surveillance. If you observe, for example, that the unit remained within specification through at least 3 calibrations performed in a 12-month time frame.?

Also, you may want to look at how critical is the product you are monitoring, and if your application allows a lower accuracy than your logger’ specifications. Do you also have another measuring device in your equipment that is more accurate than the logger you want to calibrate?

At last, your service provider might also be able to help you if they worked on a risk assessment and rationale for the stability of their products over time.

Most of the time, questioning the calibration interval is based on a financial objective, to save money. But doing so will certainly raise some questions during your next audits, to detail the rationale you've based your decision on.?

In order to document enough pieces of evidence to lengthen this process, and also to monitor over time that your rationale is still valid, you might end to spend more time and money than following a simple piece of advice: make sure that your sensors and loggers are calibrated before their 1 year anniversary.?

Similar to the oil change in your car, the manufacturer will indicate to you an ideal and recommended oil change interval. Up to you and your mechanic to decide if this interval suits you according to your driving style. Personally, I believe this is the cheapest service, in the long run, to keep my car on the road for 10 years!