The measurement uncertainty in the calibration of a thermometer depends on the calibration method used, the uncertainty contri

uncertainty calculation Exapmle

Pt100 resistance thermometer is used as the working temperature standard in the calibration laboratory. Stable temperature medium is a liquid bath with a working range from -40°C to 50°C. Data acquisition is performed via multimeter and GPIB interface or RS232 interface in the personal computer data base. Ambient temperature and relative humidity is monitored during calibration in one place and its influence appropriately evaluated. Reference Pt 100 four-wired is connected to the multimeter. In many cases, the requirements for the ambient conditions - especially the ambient temperature - are given in the specifications of the electrical devices. A calibrated thermometer is also needed for the measurement of the ambient temperature. The instrument of ambient temperature is fixed close to the measuring equipment where such influence is effective. A corresponding chart is presented in figure 1.

Figure 1: PRT calibration with platinum resistance thermometer as a reference

The temperature, at which the calibration item is calibrated, is determined by measurement with the standard thermometer and by additional corrections:

where:

• 
  Tc: temperature of the thermometer to calibrate
  
• 
  Tr: temperature of the reference thermometer
  
• 
  T_{acq Tr}: correction linked with the acquisition of reference thermometer (bridge , multimeter…)
  
• 
  T_{acq Tc}: correction linked with the acquisition of reference thermometer (bridge, multimeter…)
  
• 
  Tbath: correction linked with the bath (homogeneity, time stability).
  

The corrections given in this list are in most cases not known and presumably very small. As best estimate a correction of 0K is usually assumed which is, however, affected by an uncertainty.

1.