There are many kinds of temperature instruments used for various applications. Most people are familiar with thermometers. Among thermometers, the most common is the glass thermometer.
Glass thermometers are used in hospitals and homes. It is made of a glass tube filled with working fluid like mercury or other liquid. Changes in temperature causes the working fluid to contract or expand which changes its volume. Temperature can then be determined by measuring the volume of the working fluid. As anyone who used glass thermometer will know, glass thermometers are fragile and requires a significant wait time and shaking to get accurate results. It can also be difficult to read depending on lighting conditions.
Today, glass thermometers have largely been replaced by electronic thermometers. Electronic thermometers display readings to great precision, using tenths of units. These electronic thermometers use thermistors. A thermistor is a type of resistor whose resistance is dependent on temperature. Temperature is determined by running a current through the resistor and measuring resistance
Electronic thermometers are light, compact and durable. The digital display makes it very easy to read. However, it requires a battery that must be replaced regularly. A weak battery generates inaccurate readings.
The infrared thermometers are not so common but they are very accessible to the public. These instruments are used for non-contact measurement of temperature. It is suitable for applications wherein it is impossible or dangerous to go near the object.
It reads the black body radiation of objects. Black body radiation is radiation emitted by an object with frequency distribution specific to temperature values. Due to the complex components, infrared thermometers are much more expensive than the previous two.
