# Thermometer calibration using temperature bath - Advantages of temperature bath

**URL:** <https://forumautomation.com/t/thermometer-calibration-using-temperature-bath-advantages-of-temperature-bath/6307>\
**Category:** Calibration\
**Created:** [April 27, 2019, 5:46pm UTC](https://forumautomation.com/t/thermometer-calibration-using-temperature-bath-advantages-of-temperature-bath/6307 "2019-04-27T17:46:35Z")\
**Posts on this page:** 1\
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**Author:** ![sivaranjith](https://forumautomation.com/letter_avatar_proxy/v4/letter/s/ba9def/32.png) [@sivaranjith](https://forumautomation.com/u/sivaranjith)\
**Post date:** [April 27, 2019, 5:46pm UTC](https://forumautomation.com/t/thermometer-calibration-using-temperature-bath-advantages-of-temperature-bath/6307/1 "2019-04-27T17:46:35Z")

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![temperature%20bathh](https://cdn.forumautomation.com/original/2X/8/8db1170b4e30c638f85967e91d9d4d08fbf818b0.jpeg)

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:**

 ![temperature%20bath](https://cdn.forumautomation.com/original/2X/1/1a8e393af49f371897d2b1a3fe9aa0923315d117.png)

- 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.