All Fluke Process Instruments, Raytek and Ircon spot sensors or spot pyrometers have a warranty for calibration of 1 year. This is independent of the warranty against manufacturing defects, which is often longer, in many cases up to 4 years.
However, this does not mean that the devices will drift towards being out of specification after 1 year and that a monthly recalculation of any uncertainty or error budget needs to be implemented (for 99% of applications).
Within the devices stated accuracy, there is a provision for long term stability based on extensive testing during the development cycle and after launch, thanks to close collaboration between our QA, service and engineering departments.
The long term stability specification of many of the detectors we use are in mK per year.
This is not to say that the devices are free of possible deviation - in the calculation of the temperature value or the setting of the analog output (where used).
Calibration can be affected by:
Long term exposure to elevated temperatures - close to the operating limit of the device
Vibration
Optical contamination (deposits and or scratches on the lens)
Optical damage (heat damage to lens anti-reflection coating)
Many of our devices offer the ability to adjust both the calculated temperature and the analog output.
Our general experience, is that if a sensor suffers none of the aforementioned negative effects, the calibration from year to year will remain stable, in the sense that any deviation to a standard will fall within the stated accuracy. This is not included any consideration of the uncertainty of the calibration method itself.
We also recommend that for sensors where the analog output is used, the control system inputs are calibrated using a process calibrator or signal injector or using the sensor as a signal injector using the fixed signal output function.
Additionally, considering should be given towards change in our stated accuracy specification as a function of ambient derating, where the accuracy specification has an additional offset when the sensor is above normal room temperature.
Example:
± 0.05 K / K or ± 0.05% of reading / K, whichever is greater for sensor temperatures above degrees Celsius is added to the basic accuracy statement of ± (1% of reading or 1°C), whichever is greater
Special Note:
Not all sensors are supplied with this type of accuracy or temperature coefficient specification.
Analog Output Accuracy for 2 piece designs
2 pieces sensor designs also have an additional consideration for the analog output.
Example:
mA/V output ± 1°C
(corresponds to ± 0.015 mA for the current output at 0-20 mA
or ± 0.015 mA for the current output at 4-20 mA