Dry-wells are typically calibrated by inserting a calibrated PRT into one of the wells and making adjustments to the calibrator's internal control sensor based on the readings from the PRT. This has limited value because the unique characteristics of the reference PRT, which essentially become "calibrated into" the calibrator, are often quite different from the thermometers tested by the calibrator. This is complicated by the presence of significant thermal gradients in the block and inadequate sensor immersion into blocks that are simply too short.
