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The ways of select the infrared thermometer

[2012-02-15]

Infrared temperature-measuring in product quality control and monitoring, equipment on-line fault diagnosis, safety protection and energy saving etc are playing an important role. In the past twenty years, non-contact infrared thermometer in technology is rapidly developing, with improving performance, suitable scope also expands unceasingly, the market share increased year by year.
1. Determine target size:
According to the principle of infrared thermometers can be divided into monochromatic thermometer and double lubricious thermometer. For monochromatic thermometer, temperature measurement, the target area should be measured with thermometer view. Suggestions were measured target size than 50% of view size as well. If the target is smaller than view, background radiation energy will enter the field, thus infrared thermometer would interfere with the temperature readings, causing error. Conversely, if the target is greater than colorimeter thermometer view, you won't be measured area outside the background influences.
For double-color thermometer, its temperature is composed of two independent wavelength with inner radiation energy ratio to determine. So when tested target is very small, there is no spot, measuring pathways exist on a smoke, dust, block of radiation energy have attenuation, will not affect on the measurement results. Even in energy attenuation 95 circumstance, still can assurance requirements temperature measurement precision. The target is in motion, and tiny or vibrations goal; Sometimes in view inside exercise, or may be partially remove field goal, in this condition, use double lubricious infrared thermometer is the best choice. If colorimeter and between target could not directly targeted, measurement channels bending, narrow, stumble, under such circumstances, double-color fiber-optic colorimeter is the best choice. This is due to its diameter is small, flexible, can be in bending, block and folding channel transmission irradiation energy, accordingly can measure inaccessible, conditions or near the electromagnetic field goals.
2. Determine optical resolution (distance and sensitive)
Optical resolution by D and S ratio of determination, is colorimeter to target the distance between the D and measuring spot diameter S ratios. If infrared thermometer due to environmental restricted conditions must be installed in away from goal place, and to measure small target, should choose specular learn resolution thermometer. Optical resolution is taller, namely increase D: S ratio, colorimeter cost is higher also.
3. Determine the wavelength range:
Target material of firing rate and surface properties of decision colorimeter spectral response or wavelength. For high reflectivity alloy materials, low or changes emissivity. In the drier, measurement of metal material is optimal wavelengths of near infrared, can choose 0.18-1.0μm wavelength. Other temperature area can choose 1.6μm, 2.2μm and 3.9μm wavelength. Because there are some materials in certain wavelengths is transparent, infrared energy through these materials, to this kind of material should choose specific wavelengths. Such as measuring glass internal temperature choose 10 mu m, 2.2μm and 3.9μm (measured by glass should is very thick, otherwise you will through) wavelength, Internal temperature measuring 5.0μm chooses glass; m wavelength Measuring low temperature area selects 8-14μm wavelength advisable; Be like again measurement polyethylene plastic film choose measured μm wavelength, poly vinegar class choose 4.3 μm or 7.9 μm wavelength. Thickness more than 0.4 mm chooses 8-14 μm wavelength, And like a flame of CO2 measurement with narrowband 4.24-4.3 μm wavelength, the flame with narrowband measured CO 4.64 μm wavelength, measurement of NO2 with flame 4.47 μm wavelength.
4. Sure response time:
Response time says infrared thermometer is applied to temperature change speed of response, defined as a reading of 95% of the energy to get to the final needed time, it and photoelectric detector, signal processing circuits and display system time constant of relevant. New infrared thermometer response time can reach 1ms. This than non-contact pyrometer is much faster. If the target's movement speed quickly or measure quickly heating goals, should choose fast response infrared thermometer, otherwise da is less than enough signal respond, will reduce the measurement accuracy. However, not all applications require quick response infrared thermometer. For static or target thermal process of thermal inertia, existing thermometer response time can relax the requirements. Therefore, infrared thermometer response time and measured the choice to adapt to target.