Non Linear Hysteresis Compensation Models in Temperature Transducer Calibration
Generalized Prandtl-Ishlinskii play operators linearize directional thermal hysteresis loops, cutting transducer calibration uncertainty from 90 mK down to 13 mK.
Stirred Liquid Bath
Calibration Medium
Laboratory equipment maintains a highly stable and uniform temperature environment by circulating a fluid around a testing volume. The stirred liquid bath provides the reference environment needed to compare a working sensor against a primary standard. This method is the preferred approach for high-precision thermometer calibration.
Homogeneity Control
Mechanical impellers or pumps move the fluid at a constant rate to eliminate hot or cold spots. Inside the stirred liquid bath, the temperature gradient is kept to within a few millikelvin across the entire working zone. This level of uniformity is impossible to achieve in an air furnace.
Water is used for temperatures near ambient, while silicone oils or salt solutions extend the range.
Stability Performance
Electronic controllers adjust the heater output to counteract the heat loss to the room. The stability of a stirred liquid bath is measured by the fluctuation in temperature at a single point over a long period. High-end systems can maintain a set point within one millikelvin for several hours.
This stability allows for the calibration of high-precision platinum resistance thermometers.
Safety Requirement
Fume extraction and spill containment are necessary when operating at high temperatures. As the fluid in a stirred liquid bath nears its flash point, the risk of fire increases. Over-temperature cut-off switches are mandatory to prevent the system from overheating if the primary controller fails.