What does it mean that accuracy is valid in the calibration range?

The data loggers have an operating range, ie a range within which the logger in its entirety can work, an operating range of the sensor, this is the range within which the sensor only, covers the excluded logger (therefore, excluded electronics and batteries) can work, and a calibration range, a range in which the logger is actually calibrated.
Whether the loggers are supplied with a calibration certificate included or upon request, standard calibrations are performed on fixed points that are the same for all, to make the calibration processes uniform. However, it is possible to request additional points within this standard calibration range and for some objects even beyond this range: in this case the logger calibration range is extended.
The accuracy that is declared is relative to the calibration range only as the points of the calibration curve are corrected in this precise range. Only some loggers have good accuracy even outside the calibration range, which decreases accuracy away from the extremes of the calibration range itself. These loggers are:

• S-microW
• S-Disk J
• PressureDisk

For other models the accuracy outside the calibration range is unpredictable. For this reason, when choosing the monitoring system, it is a good idea to check the calibration code and request additional points if necessary.

Example

Take for example the S-Micro L. These are its characteristics:

• operating range: -40 ° C ÷ + 140 ° C
• sensor operating range: -40 ° C ÷ + 220 ° C
• calibration range: 25 ° C ÷ + 140 ° C

This means that the logger can withstand temperatures from -40 ° C to 140 ° C. The sensor can withstand and read from -40 ° C to 220 ° C but is calibrated in the range from 25 ° C to 140 ° C. The declared accuracy of +/- 0.1 ° C is valid in the latter range and if I wanted, for example, to use it to monitor at lower temperatures I would need extra points (for example 0 ° C). Apart from the loggers mentioned above (S-MicroW, S-Disk and PressureDisk) for all others it is necessary to have an extra point at least every 25/30 ° C in order to have a good accuracy.

Note: it is possible that by extending the calibration range the accuracy is less than the declared one.