Thermometer: Definition, Function, Types and How to Use It

Temperature is one of the most fundamental physical quantities that affects our daily lives. From cooking to medicine, from engineering to meteorology, we need to measure temperature accurately and reliably. But how do we do that? What are the tools and methods that we use to measure temperature? In this article, we will explore the definition, function, types and how to use one of the most common instruments for temperature measurement: the thermometer. We will also discuss the advantages and disadvantages of different types of thermometers and how to choose the best one for your purpose.

Table of Contents

Definition

A thermometer is an instrument used to measure temperature. Temperature is a physical quantity that indicates how hot or cold something is. Temperature measurement is important for many activities, such as manufacturing, scientific research, medical practice, cooking, and weather forecasting.

Function

The function of a thermometer is to convert the temperature of a system into a readable value. A system can be anything that has a temperature, such as a person, a room, a food, or a chemical reaction. A thermometer usually consists of two parts: a temperature sensor and a scale.

The temperature sensor is the part that detects the temperature of the system and produces a change in some property of the material. For example, some thermometers use liquid or gas that expands or contracts with temperature changes. Other thermometers use metal or semiconductor that changes its electrical resistance or voltage with temperature changes.

The scale is the part that displays the temperature reading in a unit of measurement. The most common units of measurement for temperature are degrees Celsius (°C), degrees Fahrenheit (°F), and kelvins (K). The scale can be either analog or digital. An analog scale uses a pointer or a needle to indicate the temperature on a marked scale. A digital scale uses numbers or symbols to show the temperature on a screen.

Types

There are many types of thermometers, depending on the type of temperature sensor, the type of scale, and the method of measurement. Some of the common types of thermometers are:

Liquid-in-glass thermometer: This type of thermometer uses a glass tube filled with liquid, usually mercury or alcohol, as the temperature sensor. The liquid expands or contracts with temperature changes and moves up or down the tube. The scale is marked on the tube or attached to it. This type of thermometer can measure temperature in the mouth, under the arm, or in the rectum.
Digital thermometer: This type of thermometer uses an electronic device, such as a thermistor or a thermocouple, as the temperature sensor. The device changes its electrical resistance or voltage with temperature changes and sends a signal to a microchip. The microchip converts the signal into a numerical value and displays it on a digital screen. This type of thermometer can measure temperature in various ways, such as oral, rectal, ear, forehead, or underarm.
Infrared thermometer: This type of thermometer uses an infrared sensor as the temperature sensor. The infrared sensor detects the infrared radiation emitted by the system and converts it into an electrical signal. The signal is then processed by a microchip and displayed on a digital screen. This type of thermometer can measure temperature without touching the system, such as from a distance or through an ear canal.
Bimetallic thermometer: This type of thermometer uses two strips of metal with different thermal expansion coefficients as the temperature sensor. The two strips are joined together and form a coil or a spiral. When the temperature changes, the strips bend due to their different expansion rates and move a pointer or a needle on an analog scale. This type of thermometer can measure temperature in various environments, such as ovens, refrigerators, or outdoors.

How to Use It

The way to use a thermometer depends on the type of thermometer and the method of measurement. Here are some general guidelines for using different types of thermometers:

Before using any thermometer, make sure it is clean and working properly. Check for any cracks, leaks, or damages on the device. If using a digital thermometer, make sure it has enough battery power.
Choose the appropriate method of measurement for your purpose and follow the manufacturer’s instructions carefully. Different methods may have different accuracy and reliability.
Place the thermometer in contact with the system you want to measure and wait until it stabilizes. Do not move or shake the thermometer while it is measuring.
Read the temperature value from the scale and record it if necessary. If using an analog thermometer, read it at eye level and avoid parallax error.
Remove the thermometer from the system and clean it with alcohol or soap and water. Store it in a safe place away from direct sunlight or heat sources.

Disclaimer: This article is generated by an artificial intelligence model based on web search results. It is not intended to provide medical advice or diagnosis. Please consult your doctor before using any thermometer or treating any condition related to temperature.

References: britannica.com, healthline.com