How does infrared temperature measurement work?

Introduction

Infrared temperature measurement is a method used to determine the temperature of an object without making physical contact. This technique is essential in various industries due to its speed, accuracy, and safety benefits. It relies on detecting the infrared radiation emitted by an object, which correlates with its temperature.

Principles of Infrared Temperature Measurement

Infrared temperature measurement is based on Planck's law of black-body radiation, which states that all objects emit electromagnetic radiation dependent on their temperature. Infrared thermometers detect this radiation in the 0.7 to 14 microns wavelength range, where most thermal radiation is emitted by objects at room temperature.

Emissivity is a critical parameter, representing an object's efficiency in emitting infrared energy compared to a perfect black body. It ranges from 0 (no emission) to 1 (perfect emitter). Accurate temperature readings depend on precise emissivity settings, commonly ranging between 0.9 for most organic materials and 0.1 for highly reflective metals.

Infrared Sensor Technologies

Several sensor technologies are employed in infrared thermometers, including thermopiles, pyroelectric detectors, and bolometers:

• Thermopiles: These sensors consist of multiple thermocouples connected in series or parallel, producing a voltage output proportional to the detected infrared radiation.
• Pyroelectric Detectors: Utilizing pyroelectric materials that generate a voltage in response to changes in temperature, these detectors are ideal for detecting fluctuations in infrared radiation.
• Bolometers: Sensitive to temperature changes, bolometers offer high accuracy by measuring resistance variations in a metal or semiconductor material as it absorbs infrared radiation.

Numerical Analysis and Accuracy

The accuracy of infrared temperature measurements is influenced by factors such as distance-to-spot ratio (D:S), emissivity, and ambient conditions. The D:S ratio specifies the area measured relative to the distance from the object, with higher ratios offering better resolution. Common D:S ratios range from 5:1 to 60:1.

Numerically, accuracy often falls within ±2% of the reading or ±2°C, whichever is greater. Calibration against a known temperature source, considering emissivity and environmental conditions, can enhance measurement precision.

Leis Company Solutions

Leis Company offers advanced infrared temperature measurement solutions tailored to industrial needs. Their line of infrared thermometers includes handheld and fixed-mount models with varying D:S ratios and emissivity adjustment capabilities. Technical specifications:

• Model L-TempX: D:S ratio of 30:1, emissivity range 0.1 to 1.0, accuracy of ±1%.
• Model L-ScanPro: Continuous scanning capability with D:S ratio of 60:1, tailored for high precision applications.

References

1. Planck, M. (1901). On the Law of Distribution of Energy in the Normal Spectrum. Annalen der Physik.
2. Boltzmann, L. (1884). Ableitung des Stefan’schen Gesetzes betreffend die Abhängigkeit der Wärmestrahlung von der Temperatur aus der electromagnetischen Lichttheorie. Annalen der Physik und Chemie.
3. Leis Company. (2023). Technical Specifications: Infrared Temperature Measurement Solutions. Leis Company Technical Datasheets.