Handheld Infrared Thermometers: Advantages and Disadvantages

This article explores the pros and cons of handheld infrared thermometers, comparing them to traditional contact thermometers. We’ll delve into their operation and specifications.

Introduction

Normal human body temperature generally falls between 36.1°C (97°F) and 37.2°C (99°F). This can fluctuate based on age, time of day, and activity level. A fever, often triggered by infection or illness, elevates body temperature to around 38.4°C (100.4°F).

In light of recent global events, like the COVID-19 pandemic, frequent temperature checks are crucial for personal safety and preventing the spread of illness. Elevated temperatures warrant medical attention and rest.

What is an Infrared Thermometer?

A thermometer is a device that measures body temperature. Infrared thermometers utilize infrared sensors to measure body temperature by detecting emitted IR waves. This makes them a non-contact type of thermometer. Infrared rays are invisible to the human eye because their wavelengths are longer than those of visible light.

How Infrared Thermometers Work

Here’s a breakdown of how an infrared thermometer functions:

• Power On: Ensure the device is powered on. Install batteries if necessary.

• Mode Selection: Set the desired measurement mode. Typically, the default setting is for body temperature. Other modes might be available for measuring surface temperatures.

• Unit Selection: Choose the temperature unit (°C or °F) using the designated button.

• Positioning: Hold the thermometer 2-5 cm away from the forehead or body part being measured.

• Measurement: Press the measurement switch to allow infrared rays to fall on the body.

• Display: Within seconds, the thermometer displays the temperature on its LCD screen. The infrared sensor detects reflected waves from the body, generating a voltage proportional to the temperature. This voltage is calibrated to different temperature ranges.

• Temperature Indication: The device displays the temperature according to the selected unit (Celsius or Fahrenheit).

• Color-Coded Feedback: Some models use color-coded backlights to indicate different fever levels. For example:

  • 32 to 37.3°C: Green (Normal)
  • 37.4 to 38°C: Yellow (Low Fever)
  • 38.1 to 39.1°C: Red (High Fever)

  Some thermometers also use a buzzer to signal the completion of the measurement.

• Memory Recall: Previous measurements can be reviewed by pressing the “MEM” button. The memory can be cleared by holding the “MEM” button for a longer period.

Specifications of Handheld Infrared Thermometers

When selecting an infrared thermometer, consider these common features and specifications:

• Temperature Units: Should support both °C and °F.
• Measurement Speed: Aim for the lowest possible measurement time (typically 1-2 seconds).
• Ergonomics: Comfortable grip for hand-held use.
• Power Source: Battery-powered operation.
• Fever Indication: Color-coded display for normal/high/light fever.
• Mode Selection: Button to switch between body and surface temperature measurement.
• Battery Indicator: Display battery status.
• Memory: Store previous measurements.
• Auto Shut-Off: Automatically power off when left idle.

Benefits or Advantages of Infrared Thermometers

Here are the advantages of using a handheld infrared thermometer:

• Ease of Use: Simple, comfortable, and easy to take temperature measurements.
• Speed: Very fast compared to contact thermometers like thermocouples, thermistors, or RTDs (typically 1-2 seconds).
• Non-Contact: No physical contact required, making it preferable during pandemics like COVID-19 or flu outbreaks.
• Battery Saving: Most models automatically switch off to conserve battery life after a period of inactivity (around 15 seconds).
• Portability: Lightweight and compact in size.
• Reduced Contamination Risk: Non-contact operation eliminates the risk of contamination.
• Accessibility: Can be used to measure the temperature of inaccessible objects.
• Accuracy: Comparable accuracy to contact thermometers.
• Affordability: Available at a reasonable cost.
• Measures Moving Objects: Able to measure the temperature of moving objects.

Drawbacks or Disadvantages of Infrared Thermometers

Here are the disadvantages to consider:

• Eye Safety: High-powered infrared waves can be harmful to the eyes. Exercise caution during measurements, carefully aiming at the forehead, hand, or other body parts.
• Line of Sight Requirement: Accurate measurements require a clear line of sight between the device and the surface being measured. Also, the short range means the device needs to be close to the target.
• Limited Applications: Best suited for body and surface measurements, not ideal for liquids or gases, which require specialized thermometers.
• Environmental Sensitivity: A clean environment is necessary for accurate readings.
• Variable Accuracy: Measurement accuracy varies depending on the model and price range.

Comparison: Contact Thermometer vs. Non-Contact Infrared Thermometer

The following table compares contact and non-contact thermometers based on various parameters: