Thermometer calibration using temperature bath - Advantages of temperature bath


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The thermometer can be calibrated using a comparison method using temperature baths. Temperature measuring devices are dipped in the temperature bath along with reference thermometer and they are compared.

The power provided for the heater is a few watts more than required to keep the bath stable, so the bath temperature rises very slowly and steadily.

Calibrating procedure:

Calibration setup:

  • The calibration bath is first heated to a few degrees below 100 ° C and then the thermometers are in the bath, with the mercury column just visible above the surface of the oil.

  • The bath heater is adjusted to bring the bath slowly through the 100 ° C mark once the telescope is positioned and the operator is ready to record the results.

  • Readings start once the reference thermometers show that the temperature is within approximately three divisions of 100 ° C.

  • A wristwatch with an alarm indicating 10 second intervals is used to alert the operator to take a reading.

  • The values of the reference thermometer and the thermometers being calibrated are tabulated in the columns.

Once the comparisons at 100 °C and 101 °C are complete, the thermometers are removed from the bath, cleaned to remove the oil.

Advantages of temperature bath:

  • The measurements are taken at temperatures randomly distributed across multiple divisions to ensure that the markings of bore and scale are well sampled.

  • The technique has a relatively low cost and is quicker than the fixed-temperature technique described.

  • The column of mercury rises steadily as the temperature rises, ensuring the proper shape of the mercury meniscus.

  • By using stirred alcohol baths, initially cooled with dry ice or liquid nitrogen, the technique allows temperatures down to −80 ° C without the need for coolers.