BAPI Recommended Thermistor and RTD Transmitter Calibration Interval – Application Note


BAPI certifies that Thermistor and RTD temperature sensors have been produced, inspected, and tested in compliance with applicable drawings, specifications, and standards by the manufacturer.  The product meets or exceeds published specifications and has been calibrated using applicable quality standards, such as but not limited to, the National Institute of Standards and Technology, natural physical constants, or established ratio type self-calibration techniques.

However, some uses require re-certifications or re-calibration according to the manufacturer’s recommendations.  This document shall serve notice that under the normal operating conditions (relatively clean) all sensors drift slightly with time and installation conditions.  Due to normal drift, BAPI recommends that any passive RTD or Thermistor should be tested and re-certified after 5 years.  Passive sensors cannot be re-calibrated so a three point NIST certification certificate is recommended.  Due to unpredictable field conditions, this procedure can only be done at the factory in laboratory conditions using NIST traceable equipment, procedures and standards.

The expected drift for BAPI sensors is very small and is predictable per the following specifications. However, a corrective offset calibration can be done in the field using a trusted hand held reference (Preferably NIST traceable) and offset adjustment at the controller.

Thermistors

Stability (Drift) :
Less than 0.0111°F (0.02°C) /Year.
Thermistor’s get more stable with time.

Platinum RTD’s

Stability (Drift):
Less than 0.25ºF (0.14°C) / Year @400°C for 6,000 hours.
At standard HVAC temperatures,  the drift is essentially 0°C

 

If you have any questions, please contact your BAPI representative.


Printable pdf Version of this Application Note

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