Each T-Node uses a bandgap-based digital temperature sensor subject to a precision factory calibration for NIST (National Institute of Standards and Technology) traceable temperature measurements. Calibration data remains stored at the factory and is presented to the end-user in the form of a calibration card provided with each temperature sensor. Records can be referenced via the serial number engraved on each sensor.
Determination of Coefficients
Quadratic equations unique to each temperature sensor are employed to ensure sensor accuracies of ±0.1ºC. Coefficients a, b, and c are determined from a stepwise calibration process over a 50 to 0ºC temperature range. Readings are then verified for accuracy by reversing the calibration procedure and analyzing the resulting data sets.
Note that temperature readings from degrees Celsius take place in iChart software following data collection and temperature measurement processing.
Although T-Nodes are capable of holding the initial factory calibration indefinitely, temperature strings may be sent in for a factory recalibration every two years to ensure maximum sensor performance.