What is a thermometer? What is a thermometer used for? What are the most commonly used types?
In this article, we'll try to explain the different types of thermometers and the strengths of each type.
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Having shown many weak points, the world needed something to take its place. The obvious choice is the more accurate electronic thermometer.
Regulatory bodies, institutional kitchens and food production operations have come to rely on the electronic thermometer, which includes a wide choice of the versatile thermocouple, with its impressive variety of probes for every conceivable application, as well as the highly accurate thermistor or resistance thermometers (Pt 100, pt1000).
These devices are relied on to measure the temperature of most operational activities in industry (food, pharmaceuticals, aeronautics, warehousing, automotive...)
Thermocouple thermometers are the most widely used temperature-measuring devices in process and quality control applications. In appearance, their larger size distinguishes them from their smaller cousins, thermistors.
Thermocouples are generally made up of two components: a hand-held control unit that features an on/off switch and displays the temperature in an LED window, and the probe, which is usually attached by a wire and blade connector.
The heart of the thermocouple is two dissimilar alloy strips or wires that are connected at one end. Variations in temperature at the junction of these different metals induce a change in electromotive force (EMF) between the other ends of the strips or wires.
Basically, thermocouples produce a direct current (DC), the output voltage of which changes with a change in temperature. As the temperature rises, the EMF output increases. Two types of thermocouple are suitable for our work.
The first is the type K (chrome / nickel) thermocouple. Overall, this is the best general-purpose unit because of its wide measuring range. It is ideal for use in high-humidity atmospheres and on materials with a high moisture content.
The type T (copper / constantan) thermocouple is particularly suitable for measuring low and sub-zero temperatures, and when used in atmospheres with high moisture content. It is therefore ideal for use in cold stores and freezer racks, and surprisingly, for measuring ambient temperature in buildings.
The "type" of a thermocouple has to do with the types of metal used to manufacture the probe's sensor.
The K-type probe is only compatible with a K-type instrument; the same applies to the T-type thermocouple. Among electronic temperature measurement devices, thermocouple thermometers are the most difficult to engineer. Thermocouples themselves have three distinct disadvantages, which the design and manufacture of the instrument must compensate for.
Consequently, it can truly be said that you get what you pay for: the more expensive, the better the unit.
Accuracy and performance are directly proportional to the cost of the unit.
The best units available have a total system accuracy (which is, the accuracy of the probe and instrument combined) of ± 0.5°C.
As a suggestion: if you're already spending money on an accurate instrument, you may want to ensure its continued usefulness by sending it back to the manufacturer for annual recalibration, and remember to validate its temperature frequently.
Thermocouples have excellent response times and are very durable. For any given type of thermocouple, such as K- or T-type, the output voltage versus temperature can be characterized and is highly reproducible.
This means that a wide variety of thermocouple probes can be used with the same instrument, even if the probe geometry differs.
For example, my temperature kit has nine probes to measure the temperature of everything from hot frying oil to frozen meat, from ovens to dishwashers to the tops of grills to hamburgers and chicken wings.
What's more, thermocouples can be used over a wide temperature range. This feature makes them ideal for assessing the full range of temperatures encountered in food storage, preparation and serving.
Portable thermocouple thermometers are larger and heavier than other food thermometers, and are normally powered by either AAA, AA or 9V batteries, with a typical life of around 500 hours.
