Oh no! The logger has recorded a temperature of -5°. All our vaccines are ruined and will have to be destroyed!
Hold on for a second and let’s think about this logically.
So we have a physically unlikely cooling followed by a physically unlikely warming.
Or we have a malfunction with the logger.
If this single reading was to be ignored, the shape of the graph is totally consistent.
Therefore, taking everything into account, the only logical course of action is to ignore the outlier.
Since the spike is a one-off, it’s hard to determine the cause, but here are some possible culprits…
Low battery
The most likely cause is a low battery. The logger relies on getting a constant voltage from the battery in order to product accurate temperature measurements. If the battery is starting to die, it may pass an inconsistent voltage to logger, resulting in an inaccurate reading. Even if the Battery Status was OK, this would still be our best guess.
An electronic spike from a probe
If the logger uses a probe, it may not be connected correctly, or it may be faulty. Maybe even just bumping it could produce the spike.
Room temperature
If your spike is a high temperature, rather than a low one, it may be that the logger was out of the fridge or freezer and recorded a room temperature reading, before being returned to the cold environment.
On the basis of the data around the reading, the reading is obviously false and can be classified as a misread. There has been no compromise to the quality of the fridge’s contents.
If this is a one-off event, ignore it completely. If it happens a number of times, replace the LogTag.
Loggers are sensitive electronic instruments, and sometimes they can experience interference. In the graph above, we can see “temperatures” jumping around in improbable ways. In one section, the readings jump from -8.5° to 3.5° and back to -2.5° in the space of 10 minutes. This behaviour is indicative of a faulty temperature sensor, not a faulty fridge.
While LogTag are extremely reliable and these situations are rare, it is helpful to be able to diagnose what is and isn’t possible for a fridge using your common sense.
As in the graph at the top of the page, the key is looking at the data on either side of the problem.
In the graph above, there is a problem that should not be ignored – this freezer has experienced a power failure. The difference between this and the graph above is the readings behave in an reasonable way. The temperature is not jumping around all over the place, it is rising in a regular steps as the freezer warms up.
Latency, when it comes to temperature logging, refers to the delay between a change in temperature and when that change is detected and recorded by the logger. This delay can be due to the sensor’s design, the materials it’s placed in, or the logging interval. While it might sound like a disadvantage, latency can actually serve a useful purpose in certain environments—particularly where short-term temperature spikes are common but not harmful.
For example, in a busy commercial fridge, the temperature may briefly rise every time the door is opened. A logger with high latency won’t immediately react to these short fluctuations, helping to avoid unnecessary alarms or false data indicating a problem when there isn’t one. In these cases, a slight delay in response acts like a filter, focusing attention on real issues—such as prolonged exposure to unsafe temperatures—while ignoring the everyday ups and downs that don’t affect product quality or safety.
Depending on the type of logger you have, connecting your logger to your PC means either:
First Generation LogTags use a separate Reader (sometimes called a dock) for configuration and for downloading recorded data.
The Second Generation loggers only require a USB port or cable. Apart from saving the cost of the Reader, this makes them much better suited for shipping, because the recipient doesn’t need a LogTag Reader to download a report about the shipment’s journey.
