Some Triatek systems have field calibration features, such as the FMS-1650L. However, none of the field calibration processes have the ability to calibrate the sensor with controlled air throughout the entire range of the sensor and at 20 points of scale.
Therefore, a factory calibration ensures the sensor linearization is accurate throughout the entire range of sensitivity. In contrast, the field calibration allows you to set a zero differential reference and a single differential pressure. To do this you must have an anemometer to measure DP and provide an accurate differential pressure to reference.