What is the best type of thermometer? (FAQ - Thermal)
The best thermometer to use in a particular application is something that only you can decide. Your choice will depend on many factors and a selection of these is listed below. However, the procedure for deciding on the optimum choice for any particular situation cannot be written down concisely. Simple advice can be obtained by contacting us, but if this is not sufficient then NPL staff are able to supply consultancy services.
Things to consider·
- The temperature range to be covered
- How well the temperature must be known
- Cost
- Other factors, e.g. ruggedness, speed of response, etc.
What is the smallest temperature change you need to record?
For many applications knowledge of the temperature to within 1 ºC is sufficient. The more accurately you wish to know the temperature, the more care and the greater expense you will incur.
How well the temperature must be known
If one needs to know the temperature only to within a few degrees, then it may be possible to use uncalibrated sensors of many sorts to produce estimates of temperature. For example, for many purposes an essentially uncalibrated off-the-shelf platinum resistance sensor or thermocouple should be able to determine temperature to within a few degrees from around -200 ºC to + 200 ºC with relative ease. However, if you wish to be confident that the temperature of your process or experiment is within, say, 0.5 ºC of one specified, then in general you will need to have your sensors (and your entire measurement system) calibrated at a UKAS accredited laboratory.
Other factors
Over the years solutions have been found to temperature measurement problems in an astonishing variety of challenging situations. For example, to measure the internal temperature of a person or animal there are 'pills' which are swallowed and which send radio signals indicating the temperature inside the person or animal. Similarly, it is possible to measure the temperature of molten steel at around 1600 ºC to within a few Celsius using disposable thermocouple probes. Thus it is likely that a solution to your particular temperature measurement problem already exists, but that you don't know about it. Staff at NPL have a wide variety of measurement experience and will be happy to help with your queries if you would like to contact us.