There are many different types of thermometer on the market. Whether you're checking the temperature of food and drinks, monitoring room or outdoor temperatures at the workplace, choosing a thermometer for a child's medical kit, or taking critically important industrial measurements, it's vitally important to choose the thermometer(s) best suited to the job at hand.
In today's market, more thermometers are used without firstly being checked for traceable accuracy, or suitability of purpose, yet the accuracy and suitability of your thermometer to its intended application could be the difference between passing and failing a health & safety audit, wasting a whole industrial process, or being correct the first time.
When you're choosing a thermometer, it's important to understand its associated application, temperature measurement range, resolution, accuracy, and the maintenance required to achieve repeatable measurements. Some applications will require you to achieve a much more accurate reading than others. You'll also need to consider the environment in which the thermometer is used. In a professional environment, the accuracy of your reading will ultimately affect the credibility of your future measurements, and organisation as a whole.
So, let's briefly consider the types of thermometer on the market, and their accredited application(s).
Traditional Thermometers (Spirit Filled)
Often the cheapest and most popular type of thermometer, these are ideal for use at home or in non-specialist environments where traceable accuracy is not required. They have a spirit level indication, are easy to read, and typically measure in both degrees C and degrees F. They can often be wall mounted or submerged in liquids, and require very little maintenance. These thermometers have variable measurement ranges, resolutions and accuracy.
Dual Sensor / Multiple Sensor Thermometers
Often used in a professional environment, these thermometers allow the simultaneous monitoring of two or more environments over both short and long periods of time. They are ideal for applications such as indoor and outdoor temperature comparisons, the monitoring of storage areas, and classroom maintenance. A package normally consists of a main display unit and external temperature sensors. Each external sensor reading is displayed on the main unit. The main unit can typically be wall or desk mounted, and traceable accuracy is recommended. These thermometers have variable measurement ranges, resolutions and accuracy.
Irreversible Temperature Labels
Temperature indicator labels are self-adhesive temperature proofing foils. They are ideal for use in processes where specific temperature values need to be achieved, such as sterilisation. They are also suitable for use where temperature values should not be exceeded, such as engine or bearing monitoring. They are a relatively cheap, yet effective way to achieve permanent records of accuracy. Each foil segment on a label is sensitive to a different temperature and when exposed to its rating will turn black. Each segment has both °C and °F temperature values. Each label is oil and water resistant, and the colour change is irreversible even after the object being measured cools down. After use, labels can be removed. These thermometers have variable measurement ranges, resolutions and accuracy.
Fixed & Wired Probe Thermometers
Fixed probe thermometers are designed to deliver instant temperature readings of foods, liquids and semi-solid samples via its fixed probe, which will be suitable for both immersion and penetration. They are ideal for use in the catering trade for hygiene testing, retail outlets, and laboratories. Being very easy to use and highly portable, probes will vary in size, material, and manoeuvrability. Wired probe thermometers are similar to fixed probe thermometers, the difference being that the probe is attached to the thermometer via a wire. This maximises utility without compromising accuracy. Traceable accuracy is recommended if used in a professional environment. These thermometers have variable measurement ranges, resolutions and accuracy.
K-Type thermometers deal with extreme temperatures and are normally found in laboratories and industry. They cater for applications requiring high precision, and can facilitate a range of interchangeable plug in probes for air, liquid, penetration and surface temperature measurements. They're often the best choice of thermometer if you have several applications in one professional environment. They offer wide temperature measurement ranges, high accuracy, and fast measurement response times. Non-slip function buttons and impact-resistant casing make these thermometers ideal for use in harsh working environments. Probes will vary in size, material, and manoeuvrability, and traceable accuracy is recommended if used in a professional environment. These thermometers have variable measurement ranges, resolutions and accuracy.
Data Logging Thermometers
Data logging thermometers allow continuous temperature measurements to be displayed in real-time, or downloaded and stored to PCs or Laptop computers. They are designed to record temperature history in critical areas such as storage rooms, transportation, and laboratories, and are ideal if you'd like to submit regular records to management, auditors, or work colleagues. The recorded measurements can be attached to emails or reports, and is great for fault finding or traceability in controlled environments. A user may select the logging rate, start time, alarm limits, and logging mode. The supplied analysis software provides a graphical display of data, showcasing the total readings, a zoom facility for individual readings, and a visual indication of alarm levels throughout the logging period. Traceable accuracy is recommended if used in a professional environment, and again, these thermometers have variable measurement ranges, resolutions and accuracy.
Infrared thermometers are designed for non-contact measurement of very high / low surface temperatures, and are frequently equipped with a laser to measure radiated heat. They are suitable for temperature measurements of air conditioning systems, transport and automotive spot checks, and food preparation surfaces. It's not as simple to operate these thermometers as some suppliers would have you believe. It's not point; pull the trigger, read the measurement. Important factors to consider before measuring are laser spot-size, and the emissivity value of the surface being measured. The error in the accuracy of a measured value can be as much as 30% of the reading just based on emissivity. Traceable accuracy is recommended if used in a professional environment. These thermometers have variable measurement ranges, resolutions and accuracy.
Thermal Image Cameras
Thermal image cameras allow immediate identification of hot and cold areas via thermal imagery. They are ideal for detecting hidden problems, surveying buildings to find moisture and leaks, identifying energy loss and poor insulation, electrical faults, and detecting plumbing issues. Some cameras facilitate the download of imagery to PCs or Laptop computers. The recorded data can then be attached to emails or reports, and is great for fault finding or traceability in controlled environments. Some models include a correction for emissivity and reflected temperature. Again, there will be variable measurement ranges, resolutions and accuracy.
If you can choose the thermometer best suited to your intended application, AND provide traceable instrument calibration to an auditor, you can always be assured of your measurement's creditability. If you're unsure of a thermometer's suitability, always consult the help of a professional body.