Contact vs. Non-Contact Thermometers: A Detailed Comparison

This article compares contact thermometers and non-contact infrared thermometers, highlighting the differences between them and the advantages of non-contact infrared thermometers.

Introduction

Temperature measurement is a common practice across various industries, including:

• Medical
• Mechanical
• Civil
• Manufacturing
• Quality Control
• Food Processing
• Agriculture

Temperature monitoring is crucial for maintaining the quality of perishable goods, fruits, and vegetables from their origin through transportation and to their final destination. Traditionally, this monitoring has been done using various types of contact thermometers.

More recently, with the onset of pandemics like COVID-19, frequent body temperature checks have become essential for identifying potential illness or infection. Due to the contagious nature of such diseases, maintaining a safe distance (around 6 feet) during temperature measurement is important. This need has led to the increased use of non-contact infrared thermometers.

Contact Thermometer

A contact thermometer requires physical contact with the object being measured. Different types of contact thermometers are available for measuring the temperature of:

• Food
• Liquids
• Semi-solids
• Surfaces
• Air
• Human Body

These thermometers typically operate based on the principles of thermocouples, Resistance Temperature Detectors (RTDs), and thermistors. Because they often use external probes, they are also known as probe thermometers.

Contact thermometers work by conduction, a heat transfer mechanism. Figure 1 shows a pocket-type food thermometer and a digital thermometer used for measuring body temperature in cases of fever.

Advantages of Contact Thermometers

Here are some benefits of using contact thermometers:

• Accuracy: Provides very accurate temperature measurements due to direct surface or body contact.
• Wide Range: Offers a wide temperature measurement range.
• Response Time: Offers a short measurement response time.
• Cost-Effective: Inexpensive and affordable.
• Robustness: Can operate in hazardous and unclean environments due to its contact-based operation.

Non-contact Infrared Thermometer

A non-contact thermometer does not require any physical contact with the object being measured. It uses an infrared sensor to detect and measure infrared waves emitted from the object. These infrared rays are invisible to the human eye and have wavelengths longer than visible light.

Figure 2 shows a typical non-contact infrared thermometer. These devices are usually battery-powered and designed for handheld use. They can measure body or surface temperature from a distance. These thermometers are useful for quickly assessing patients for fever, indicating whether the temperature is high, low, or normal.

Advantages of Infrared Thermometers over Contact Thermometers

The following points highlight the advantages of infrared thermometers over contact thermometers:

• Safety: Can measure extreme temperatures without posing safety risks.
• Speed: Quick and fast temperature measurements with the pull of a trigger.
• Hygiene: No risk of contamination due to its non-contact functionality.
• Portability: Lightweight and compact in size.
• Accessibility: Can measure the temperature of inaccessible objects or surface parts.

Difference Between Contact Thermometer and Non-contact Infrared Thermometer

The following table provides a comparison between contact thermometers and non-contact infrared thermometers.