Thermometer (thermos: hot; metron: measure) is the universal instrument used to measure temperature. Temperature and heat are two words which often confuses people. For example, how do you explain the hotness of an object? What is the measure or basis for that hotness? The answer to that is temperature. Heat is a form of energy and its unit is Joules. On the other hand, Temperature is the measure of that heat. Which means, if the heat is more, the temperature is more as well. But how do we measure temperature? We use a device called thermometer to measure the temperature of any object.
By definition, the temperature is the measurable extent of hotness or coldness. It is a mathematical representation of heat. There are different units to measure temperature, like Celsius (˚C), Kelvin (K) and Fahrenheit (˚F).
There are different types of thermometers according to the needs. For example, there are one set of thermometers which is used to measure body temperature while another set of thermometers to measure boiling point and freezing point during experiments. Here, we will discuss the two types of thermometers, namely, clinical thermometer and laboratory thermometer.
Clinical thermometers are meant for clinical purposes. It is developed for measuring the human body temperature. It is a long narrow glass tube with a bulb containing mercury at the end. The normal human body temperature is 37˚C; which can fluctuate between the ranges 35˚C to 42˚C. Hence, the clinical thermometers have the range 35˚C to 42˚C. The level of mercury tells our body temperature in ˚C. Since mercury is a toxic element, thus these thermometers have been replaced by digital thermometers nowadays.
Note: Clinical thermometers must be sterilized before use for the safe and clean check-up.
Since clinical thermometers can’t be used to measure temperature other than the human body, we need a special type of thermometers for other purposes. A laboratory thermometer, which is colloquially known as the lab thermometer, is used for measuring temperatures other than the human body temperature. It ranges from -10˚C to 110˚C. Laboratory thermometers are designed for lab purposes such as checking boiling point, freezing point, or temperature of other substances. You can use a laboratory thermometer for checking the temperature of a solvent but not a clinical one.
Weather reporters also use maximum-minimum thermometers for measuring maximum and minimum temperatures of a place.