Appendices | B |
Basics of Infrared Measurement |
Q. What is the distance to spot ratio?
A. The optical system of an infrared thermometer collects the infrared energy from a circular measurement spot and focuses it on the detector. Optical resolution is defined by the ratio of the distance from instrument to the object compared to the size of the spot being measured (D:S ratio). The larger the ratio number the better the instrument’s resolution, and the smaller the spot size that can be measured. The laser sighting included in some instruments only helps to aim at the measured spot.
A recent innovation in infrared optics is the addition of a Close Focus feature, which provides accurate measurement of small target areas without including unwanted background temperatures.
Make sure that the target is larger than the spot size the unit is measuring. The smaller the target, the closer you should be to it. When accuracy is critical make sure that the target is at least twice as large as the spot size.
Q. How to take temperature measurement?
A. To take a temperature measurement, just point the unit at the object you wish to measure. Be sure to consider
•Measure surface temperature only. The IR thermometer cannot measure internal temperatures.
•Do not take temperature measurement through glass. Glass has very distinctive reflection and transmission properties that do not allow accurate infrared temperature reading. Infrared thermometers are not recommended for use in measuring shiny or polished metal surfaces (stainless steel, aluminum, etc.). (See Emissivity.)
•Watch for environmental conditions. Steam, dust, smoke, etc., can prevent accurate measurement by obstructing the unit’s optics.
•Watch for ambient temperatures. If the thermometer is exposed to abrupt ambient temperature differences of 10 degrees or more, allow it to adjust to the new ambient temperature for at least twenty minutes.
Q.What are some uses for non-contact thermometers?.
A.The most popular uses include:
•Predictive and Preventive Industrial Maintenance: check transformers, electrical panels, connectors, switchgear, rotating equipment, furnaces and much more.
•Automotive: Diagnose cylinder heads and heating/cooling systems.
•HVAC/R: Monitor air stratification, supply/return registers and furnace performance.
•Food Service & Safety: Scan holding, serving, and storage temperatures.
•Process Control & Monitoring: check process temperature of steel, glass, plastics, cement, paper, food & beverage
For additional information on applications for