When a thermometer is heated, the liquid within the bulb expands and is forced upward into the capillary where its level indicates the temperature value. Each heating and cooling cycle imparts tremendous stress to the bulb. After repeated use, even the highest quality liquid in glass thermometer will undergo a slight change in bulb volume due to this expansion and contraction.
When a change of this type does take place, the indication of the thermometer will also change. Re-calibration of the certified thermometer updates the indications and thus allows the user to maintain accurate, reliable and consistent results when making temperature measurements.
Re-calibration at regular intervals to document traceability to NIST is an important part of most quality programs such as the ISO series of quality standards, to assure that required levels of accuracy are being met. The amount of change which will occur in a given period of time say one year is a factor of how well made the instrument is, the particulars of the testing for which it is used, and the frequency with which the instrument is utilized.
For example, from our experience, thermometers used in air or in non-aggressive liquids, at temperatures around room temperature, tend to experience relatively small changes. These range from the in-house calibration laboratory to accredited calibration laboratories and the national meteorological institute. Frequently, measurement technology manufacturers also have such facilities themselves. They work independently of product and are able to carry out complex services.
These range from checking a working standard to calibrating customer-specific designs such as pre-assembled multipoint thermometers. Together, the quality management of the customer and the laboratory can develop the calibration processes necessary for a plant. It is necessary to define where standard checks are sufficient, where customer-specific solutions make sense, or whether downtime in the process should be reduced by using a certified mobile calibration laboratory.
For this, the customer contacts the laboratory to define the relevant temperature points and measurement uncertainties. These are used to derive the equipment that must be used for the calibration. In general, a distinction is made between two methods when calibrating thermometers — the fixed-point calibration and the comparative calibration.
WIKA offers both fixed-point calibration and comparative calibration. The appropriate calibration method is determined by the requirement for accuracy and the type of test item. For the certificates, the choice can be made between a 3. Save my name, email, and website in this browser for the next time I comment. Kasy Allen is the owner and lead marketing strategist of Annapurna Digital , a digital marketing agency.
In addition to working with Tundra Restaurant Supply with their online marketing strategies, Kasy has helped many online brands find their online voice and an online marketing strategy that brings in the right users and increased revenue.
For that perfect medium rare, you're going to need a tool that perfectly measures the temperature of the steak. Since we're not all so lucky to own the world's best and most accurate thermometer —which, btw, you should think about treating yourself to one—you're going to have to learn how to test and adjust your thermometer so it's backyard barbecue ready.
Here's how:. Just like watches can run slow or fast, food thermometers are subject to inaccuracies with age and use. Thermometer accuracy can be affected by extreme temperature changes, like going from extremely hot food to cold food, or by being dropped or roughly handled.
And if you're using your thermometer frequently, you may want to check it monthly just to make sure it's performing at its best. Luckily, you can test the accuracy of your thermometer and, in most cases, calibrate it to read accurately again. Many thermometers have a nut under their temperature dial that allows them to be adjusted, while most digital models have a reset button.
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