Temperature profile characterization of baths in three dimensions

Traceable temperature measurements require that temperature sensors should be regularlycalibrated with respect to the internationally agreed temperature standards . To do this,two methods are used i.e comparison calibrations and fixed point calibrations. The latteris the most common method used by secondary temperature calibration laboratories.Liquid baths are the main calibration equipment that directly affect the measurementuncertainty in temperature calibrations. Therefore, the characteristics of baths need to bewell investigated and understood.The temperature profile and stability of liquid baths are one of the most importantcontributions to the calibration uncertainty of platinum resistance thermometers, digitalthermometers, liquid-in glass thermometers, thermocouples and etc. .In general, commercial baths only present a two-dimensional bath profile or sometimejust a stability of the baths are given However, thermometers, thermocouples and etc. areimmersed into the body of the bath. Thus the depth or z axis is also very important.In this work a measurement system has been designed using three-stepper motors and adata acquisition system (DAS). The DAS is developed using object oriented algorithmscalled a three dimensional (3-D) scanning system. The 3-D scanning system is homemadeand used in conjunction with a Hart Scientific reference platinum thermometer, thetemperature profiles and stability of several types of baths: water, oil and salt werecarried out in the temperature range 30 °C to 450 °C. This will then contribute towards amore accurate uncertainty budget.