Non-Contact Thermometers Technical Guide
Every material emits infrared ray. The higher temperature the material is, the stronger infrared ray it emits.
Non-contact thermometer measures the amount of infrared ray and calculate the temperature of the material.
2. FOV (Field Of View) and measuring distance
Non-contact thermometer measures average temperature of the area in the FOV. FOV changes according to the measuring distance from the sensor to the target object. To measure the temperature of the target object, the target object must be big enough to fill the FOV.
3. Maximum measuring distance
Basically, the longer distance, the wider FOV though, longer distance means that influence of the atmospheric condition e.g. dust in the air, humidity, noise from background, etc. will be bigger.
4. Measurable objects
Basically, non-contact thermometer can measure temperature of surface of solid or liquid objects. It can't measure temperature of gas, flame nor inside of solid or liquid objects. Following show example conditions that the non-contact thermometer can't measure the temperature.
Glossy metal surface
When the surface is very glossy, infrared radiation is very small and also it reflects infrared ray emitted by other materials. Stable measurement won't be possible in this case.
Trough glass plate
Visible light can go through glass though, infrared can't. In this case, the temperature of the glass surface will be measured.
5. Detecting wavelength
To get better measurement result of the temperature, we have to consider absorption of infrared ray by water vapor (H2O) and carbon dioxide (CO2) in the atmosphere. In that sense, OPTEX-FA's non-contact thermometers utilize infrared with its wavelength from 8 to 14 µm shown as following. This range of wavelength is one of the widest ranges of wavelength called infrared atmospheric window.
6. Influence of dust
When you can see the target object clearly, measurement of temperature will be done correctly though, if you can't see the target object because of dust in the air or if the lens of the non-contact thermometer is contaminated, measurement of temperature won't be correct. In case the lens is contaminated, please clean the lens. For mounted type, please utilize option air purging pipe to keep the lens clean.
7. Influence of water vapor
OPTEX-FA's non-contact thermometers is utilizing infrared atmospheric window range though, if you can't see the target because of too much water vapor, measurement result won't be correct.
8. Measurement from angled direction
Even if the non-contact thermometer is angled, as long as the target object is big enough to cover its FOV, it will be able to measure its temperature correctly. Although, if the angle exceeds 45 degree, it won't be able to measure the temperature correctly.
9. Measurement temperature of the object turning
Non-contact thermometer can measure the temperature of objects turning because it doesn't touch the object. Measured temperature will be average temperature of the objects in the FOV while sensors response period.
10. Flatness of measurement target
Non-contact thermometer measure average temperature of the target in the FOV area so flatness is not important for the measurement.
11. Influence of target color
Non-contact thermometer won't get any influence by color of target objects. Although, it will get influence when the surface of the target object is glossy (metallic paint for example).
12. Measurement in the dark
Non-contact thermometer receive infrared ray so measurement in the dark is not a problem.
13. Laser for alignment
OPTEX-FA's non-contact thermometers uses Class 2 laser (JIS C 6802) fro alignment so don't stare into laser beam or point laser beam at eyes since it may damage the eyesight.
14. Measurement of temperature of human body
Don't use OPTEX-FA's non-contact thermometers for medical purpose nor measuring human body temperature.