How cold chain logger calibration works in Australia: what it checks, how often to repeat it, and what a NATA certificate should show before an audit.
Cold chain logger calibration compares your logger’s readings with a reference thermometer that has a current traceable certificate. It records how far the logger is off at each test point. For a 2 °C to 8 °C fridge, you want a multi-point calibration, ideally from a NATA-accredited laboratory, repeated on a schedule set by your risk, your regulator and the logger’s manufacturer. A calibration certificate proves the logger was accurate on the day it was tested. It does not prove what happened in your fridge last night.
This guide is for quality managers, pharmacy and clinic staff, food producers and laboratory teams who rely on data loggers to prove product stayed in range. We cover what calibration checks, how it is done, how often, what a certificate should contain and how to avoid the gaps that auditors find.
A logger drifts. Sensors age, batteries are swapped, units get dropped in a esky or left in a hot vehicle. Calibration finds out by how much. A qualified technician exposes the logger and a reference thermometer to the same stable temperature, then records the difference.
WHO says calibration checks a temperature device against appropriate standards over its full operating range. It should ideally be a documented three-point calibration by a nationally or internationally accredited laboratory. An ice-water check is only a one-point alternative when full calibration is unavailable.
These terms get mixed up on purchase orders, so keep them apart:
Calibration tells you the sensor was accurate when tested. Continuous monitoring tells you what the temperature did overnight and across a weekend. The Australian Government says vaccine data loggers can show how accurate the fridge’s own thermometer is, whether temperature fluctuated and for how long, and where cooler or warmer areas sit inside the fridge. A calibrated logger placed in a badly loaded fridge still tells you only about the spot where it sits.
The strictest everyday example is vaccine storage. The Department of Health and Aged Care states that vaccines must be kept between +2 °C and +8 °C. It also says domestic fridges, including bar fridges, are not designed for vaccine storage and are not suitable for it.
NSW Health’s cold chain guidance says data loggers should record at five-minute intervals and be downloaded weekly to check for excursions outside +2 °C to +8 °C. A logger that records often but reads 1.5 °C low can hide a real excursion, which is why calibration sits underneath the whole monitoring routine.
Food businesses face a similar expectation for handheld thermometers. The NSW Food Authority recommends calibrating thermometers at least once every six months, depending on use, and keeping calibration records.
Other cold chains, such as pharmaceutical distribution, blood and tissue, laboratory samples and food transport, set their own limits through their quality system, licence conditions or customer contracts. Check which document governs your product and read the temperature range and record-keeping clauses in it.
CSIRO’s guidance on calibrating thermometers and temperature loggers describes the principle: compare the logger with a certified reference thermometer at the temperature being checked. The practical sequence looks like this:
If a logger comes back out of tolerance, the as-found data tells you that readings before the calibration may have been wrong. That triggers a review of the product stored since the last good calibration. A certificate that shows only as-left values hides this information, so ask for both.
A quick ice-point check in a slurry of crushed ice and water is a reasonable routine check between full calibrations. Treat it as a screening tool. If a logger fails it, take the unit out of service and send it for calibration. Passing the ice point says nothing about its accuracy at 8 °C.
There is no single number that suits every site. CSIRO says calibration frequency should reflect how likely the thermometer is to drift and how important the measurement is. That makes the interval a risk decision you can defend in writing.
WHO lists the triggers for recalibration in its temperature accuracy guidance:
In practice, most sites pick a fixed calendar interval and add event-based triggers on top. A common approach is to set the routine interval in your quality procedure, then add a line stating that any drop, heat exposure or battery change triggers a check. Where a customer, licence or guideline sets a shorter interval than your own, the shorter one wins.
| Situation | Suggested approach |
|---|---|
| Vaccine fridge logger | Follow the interval in your state’s cold chain guidance and the logger manufacturer’s instructions |
| Food handheld probe | Calibrate at least every six months, depending on use, per NSW Food Authority advice |
| Pharmaceutical warehouse logger | Interval set by your quality system and risk assessment, documented |
| Logger dropped, overheated or battery replaced | Check or recalibrate before returning it to service |
| Readings that look wrong | Remove from service and calibrate |
A certificate is only useful if it matches how you use the logger. Before you book, check four things.
A logger used for 2 °C to 8 °C storage needs test points in that range. A certificate covering only 0 °C and 100 °C tells you little about 5 °C. If you ship product at frozen or ultra-low temperatures, the points must reach those temperatures too.
A logger checked against an uncalibrated reference is not calibrated in any way an auditor can accept. The reference thermometer needs a current certificate traceable to a national standard. In Australia, NATA-accredited laboratories work to ISO/IEC 17025, which is the standard for calibration laboratories. Ask which accreditation covers the temperature range you need, as accreditation applies to a defined scope.
A useful certificate shows:
Compare the deviation plus its uncertainty against the accuracy your process needs. If a logger’s error is 0.4 °C and the uncertainty is 0.2 °C, you have 0.6 °C of worst-case error to fit inside your allowed margin.
The lab reports the numbers. You decide whether the logger passes, using the manufacturer’s accuracy specification and your product’s tolerance. Write the acceptance limit into your procedure before the logger goes out, so the pass or fail decision does not depend on the result.
PCS Precision explains the audit angle in more depth in our guide to Testo data logger calibration auditors can verify, and in our note for quality managers on asking for NATA traceable data loggers.
Calibration answers one narrow question: is this sensor accurate? Mapping answers a different one: how does temperature vary across the space? A fridge or cool room can have warm and cold spots, and the logger only sees the position it occupies. A 48 to 72 hour mapping study of a storage area is one way to find where to place probes before relying on them.
A sensible sequence for a new or relocated cold room is:
We see the same pattern in cold chain audits. The business owns a good logger, the data looks tidy, and the certificate is out of date or covers the wrong range. The logger was not the problem. The system around it was.
Our view is that a NATA-accredited calibration is the most direct way to show your readings can be trusted. At PCS Precision we are NATA accredited and ISO 9001 certified, and we calibrate on site or in our workshop, whichever suits your operation. We also work across multiple equipment brands regardless of where you bought the logger, so you do not need to replace working equipment to get a defensible record.
Our advice is simple. Set the interval in writing, ask for as-found results every time, keep a spare logger, and book the next calibration before the current certificate expires. That removes most of the risk before it reaches your product.
Kaz
If you need a logger calibrated, we offer NATA calibration and wider calibration, maintenance and repair services for business customers. If you need to replace or add loggers, browse our temperature data loggers, including the Testo 175 T1, the Testo 175 T2 two channel logger and the Tinytag Ultra 2. For urgent needs, we offer 24/7 emergency support. Get in touch through our site for a tailored quote.
If you also use handheld probes or infrared units on the same cold chain, our infrared thermometer calibration guide covers the standards involved.
Yes. Sensors drift over time, and WHO lists several recalibration triggers, including certificate expiry, shock, heat exposure, battery replacement and suspect readings. Calibration is also how you show an auditor that your temperature records can be trusted.
Calibration compares the logger with a traceable reference at several points and documents the deviation. Verification, such as an ice-point check, is a quick one-point screen. NIST describes spot-checks as a first line of defence that does not replace multi-point calibration.
Requirements depend on your regulator, licence or customer. WHO says a full three-point calibration by an accredited laboratory is the ideal. A NATA-accredited calibration gives you traceability that is straightforward to defend, provided the accreditation covers your temperature range.
Set the interval by risk and by the manufacturer’s instructions, then add event triggers. CSIRO says frequency should reflect how likely drift is and how important the measurement is. For food thermometers, the NSW Food Authority recommends at least every six months, depending on use.
You can run an ice-point check as a routine screen. A full calibration needs a certified reference and a controlled environment, which is why WHO points to an accredited laboratory as the ideal.
