The temperature sensors from Disruptive Technologies offer excellent accuracy, excellent long-term stability, and continuous liveliness checks without any need for re-calibration in most use cases.
Key takeaways
- Excellent accuracy of +/- 0.5 °C measuring in the range from 0 °C to +65 °C based on factory calibration on each sensor.
- Long-Term stability of better than 0.04 °C per year results in an accuracy better than +/-1 °C, in the range 0 °C to +65 °C, after 15 years.
- The sensor reports several times per hour to the cloud, making it easy to spot and replace broken or misplaced sensors.
Accuracy over time
The temperature sensor from Disruptive Technologies is calibrated at manufacturing. Re-calibration is in many cases not required due to the excellent long-term stability of the Disruptive Technologies sensor, as shown in the graph below.
Absolute temperature accuracy versus sensor age
The temperature measurement unit in the sensor is based on CMOS technology. It is an industry-leading, fully integrated solution with excellent long-term stability. This is achieved by integrating the sensing element, readout electronics, and calibration on a single integrated circuit with a digital interface.
Calibration
Transfer standards are used in the calibration of individual sensors during manufacturing. The transfer standards are subject to scheduled calibration procedures. The calibration of the reference itself used for the calibration of the transfer standards is performed by an ISO/IEC 17025 accredited laboratory which is a full member of the International Laboratory Accreditation Cooperation (www.ilac.org). The qualification procedures used to establish accuracy and long-term stability are performed based on the JEDEC JESD47 qualification test method.
The requirement for re-calibration does, however, not only stem from the long-term stability of the sensing solution itself. In some industries, legal requirements demand checking or calibration at regular intervals. Such checks are then part of the total quality assurance system. A regular check would identify far more errors than drift in the sensor element itself. It could discover damage to the complete sensing setup and equipment. Broken mechanical assembles or measurement probes could be found, and one could even verify that the temperature sensor has not been removed or relocated.
The cloud-connected regular measurements from the Disruptive Technologies’ sensors make it easy to detect if a sensor stops reporting automatically. This will, together with the excellent long-term stability of the sensors, render most regular calibrations unnecessary.
It is possible to perform regular inspections in cases where even better reliability is required to verify the accuracy of the sensors. Inspections could be done by comparing measurements over a period with a 3rd party temperature sensor or temporarily placing a secondary, newly factory-calibrated, Disruptive Technologies temperature sensor next to the first one for some time and inspecting the temperature difference. If this difference is outside the acceptable range, then the first sensor should be replaced.
A regular re-calibration or inspection could, by the means described above, be run as follows:
- Check the setup visually and ensure correct sensor placement
- Check the difference between redundant sensors and verify that it still is within limits (if no automatic monitoring is implemented)
- Check that all sensors are reporting as expected
In cases where legal requirements demand strict regular calibrations at a certain interval, an alternative approach would be to replace the sensors with new sensors regularly. New sensors are already factory calibrated and will, therefore, be calibrated at the time of installation. Sensors should not be attached with tape in these cases but with brackets that allow the sensor to be removed without being damaged.