Temperature sensor: how do they work | isweek.com - Industry sourcing

The most basic definition of temperature sensor devices is that they are tools specially designed to measure the hotness or coolness of an object. However, sensors are actually measuring the atomic activity and movement of an object. When temperature sensor devices read an object with zero atomic activity, the temperature point is considered absolute zero. When a substance is heated, it usually moves through several phases: solid to liquid and from liquid to gas until the atomic activity begins increasing.

How temperature sensor devices measure temperature
There are four major measurement scales that are broken down and categorized into different degree units. They represent the method temperature sensing devices use to measure the molecular activity of an object.

Using the metric Celsius scale at a point of reference, the measuring scale begins at zero. Freezing water would measure zero while boiling water measures one hundred. If the Fahrenheit scale also starts with the zero measurement as the coldest object (freezing water) going from 32 degrees to boiling water measuring 212 degrees. Temperature reading devices recognize absolute zero measurements as near -460 degrees Fahrenheit. The absolute scale using Fahrenhiet temperature sensing is also called the Rankin scale. Absolute zero on the Rankin scale is 492 degrees Rankin.

Temperature measuring terminology
Understanding how temperature sensor equipment works requires that you also understand the industry terminology. For example, the accuracy of a temperature sensing device refers to how close the reading is to the actual temperature. When resolution is discussed, it is referring to the absolute smallest temperature change that will be noticed and registered on the device.

Linearity is the process of creating a record where you record how the accuracy changes showing a wide temperature range. The temperature range refers to the obvious difference between maximum and minimal temperature readings. The time constant is the amount of time it takes to measure a temperature change to accuracy. Time constants of temperature sensor devices record minutes in air, the seconds in still liquids and fraction seconds are measured in moving liquids.

A time tested temperature measuring method
There are still some older temperature sensor techniques being used by professionals today. Simple expansion is based on the principle that when most substances are heated they expand. This effect can be even greater by adding mercury or alcohol to a capillary tube which creates a well known temperature sensor device - A traditional thermometer.

Thermocouples
Thermocouples are another thermal measuring technique. A thermocouple is made from two different metals which are welded together. The combination of these two different metals has the potential to generate a powerful voltage similar in capacity to the temperature. In order to use this temperature measuring device, you would either need to add a second junction using freezing water or create an icepoint reference voltage to create resistance.

Thermocouples can be pricy and are not necessarily the easiest thermal measuring devices to work with, but many industry experts swear by these devices. These temperature sensor devices can provide some impressively diverse measurement ranges.

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