Infrared thermometers are powerful tools for quick, contact-free temperature readings, but to get truly accurate and reliable results, it's important to follow proper technique. This step-by-step guide walks you through how to use your IR thermometer effectively while avoiding common pitfalls that can lead to inaccurate measurements.

Step-by-Step Guide on Getting Great Results with an Infrared Thermometer

Step 1: Understand the Distance-to-Spot Ratio

• Always get close enough to ensure that the area being measured is smaller than or equal to your target spot.
• Check your model’s specifications for its exact ratio.

The distance-to-spot (D:S) ratio tells you how large an area your thermometer is measuring relative to your distance from the target. For example, a D:S ratio of 12:1 means you’re measuring a 1-inch diameter spot from 12 inches away. If you’re too far from a small target, your thermometer will pick up surrounding temperatures and distort your result.

Step 2: Use the Laser as a Guide, Not a Measuring Tool

• Refer to your thermometer’s manual to understand the actual size of the area being measured at various distances.
  • The laser is just an aiming aid.

The laser pointer on most infrared thermometers shows the approximate center of the measurement area—but it doesn’t define the full measurement zone. Assuming the laser represents the full area can lead to major errors, especially at longer distances where the measurement spot widens. Dual laser IR thermometers can simplify this step, allowing the user/operator/technician to determine spot size without calculating D:S.

Step 3: Account for Shiny or Reflective Surfaces

• Apply a piece of non-reflective tape (e.g., electrical tape) or flat paint to the surface before taking a reading. This gives your thermometer a better surface to measure.

Shiny materials like polished metal have low emissivity, meaning they emit less infrared radiation compared to dull or matte surfaces. Low emissivity can cause your thermometer to under-report the actual temperature.

Consideration: If your IR thermometer supports adjustable emissivity settings, match the setting to the material you're measuring. Shiny metals typically require a "Low" setting, while wood, paint, and plastic fall under "High". You can find emissivity charts and tables online for reference.

Step 4: Avoid Steam, Dust, or Obstructions

• Make sure your line of sight is clear.
  • If you must work in a dusty or steamy environment, try to get as close to the target as safely possible.

Steam, dust, or smoke between the thermometer and the target can scatter infrared energy and interfere with accurate readings. Any material between your lens and the surface can block or distort the IR signal.

Tip: Use lens cleaning wipes to keep the device clean during extended use in rough environments.

Step 5: Let the Thermometer Adjust to Its Environment

• Let the device sit in its operating environment for about 30 minutes before taking critical measurements. This allows internal components to stabilize to the local temperature.

Like any precision instrument, IR thermometers can be affected by rapid changes in ambient temperature. A thermometer stored in a cold vehicle may produce inaccurate readings when brought into a warm building—at least until it acclimates.

Step 6: Maintain Your Equipment

• Clean the lens regularly with a soft cloth or lens-safe cleaner.
• Avoid using abrasive materials or exposing the lens to sudden temperature changes.

Over time, dirt, scratches, or condensation on the thermometer’s lens can degrade performance. A clean, clear lens ensures maximum accuracy by letting the infrared energy reach the detector without interference.

Quick Recap: Best Practices for Infrared Thermometers

To consistently get great results with an infrared thermometer:

• Know your distance-to-spot ratio and stay close enough.
• Don’t rely solely on the laser pointer.
• Account for shiny or reflective surfaces.
• Keep a clear line of sight to the target.
• Allow the thermometer to adjust to its environment.
• Clean and maintain your thermometer regularly.

Used correctly, infrared thermometers offer an exceptional mix of safety, speed, and precision. By following these steps and staying aware of your surroundings and surface types, you'll get more reliable data and make smarter decisions based on accurate temperature readings.