Infrared Thermometer Selection Guide
Shanghai Wujiu Automation Equipment Co., Ltd. With the continuous improvement of scientific skills, the variety of infrared thermometers is also increasing. When purchasing, we will be helpless. Faced with so many goods, what do we do when we buy?
The engineers below will give us some advice.
When we are shopping, we usually think about the following three aspects:
1. Performance indicators, such as temperature scale, spot size, operating wavelength, measurement accuracy, response time, etc.;
2. Environmental and operating conditions, such as ambient temperature, window, display and output, maintenance accessories, etc.;
3. Other selection aspects, such as ease of use, maintenance and calibration performance, and quotation, also have a certain impact on the selection of thermometers. With the skills and continuous development, the best planning and new development of infrared thermometers provide users with a variety of functional and multi-purpose instruments, expanding the selection.
Then let us introduce you in detail:
Determine the temperature scale
The temperature measurement scale is the most important performance indicator of the thermometer. For example, TIME (Time), Raytek (Leite) goods cover the scale of -50 ° C - + 3000 ° C, but this can not be done by a type of infrared thermometer. Each type of thermometer has its own specific temperature measurement scale. Therefore, the user's measured temperature scale must be considered accurately and comprehensively, neither too narrow nor too wide. According to the black body radiation law, the change of the radiant energy caused by the temperature in the short wavelength band of the spectrum will exceed the change of the radiant energy caused by the emissivity error. Therefore, it is better to select the short wave when measuring the temperature.
Determine the policy scale
According to the principle, the infrared thermometer can be divided into a monochrome thermometer and a two-color thermometer (radiation colorimeter). Regarding the monochrome thermometer, when the temperature is measured, the area of ​​the measured guide should be filled with the field of view of the thermometer. It is better to claim that the measured policy scale exceeds 50% of the field of view. If the policy scale is smaller than the field of view, the set radiant energy will enter the thermometer's visual accumulator to disturb the temperature reading and form an error. Conversely, if the policy is greater than the field of view of the thermometer, the thermometer will not be affected by the scenery outside the measurement area.
Determine optical resolution (interval and active)
The optical resolution is determined by the ratio of D to S, which is the ratio of the interval D between the thermometer to the guide and the measured spot diameter S. If the thermometer is necessary to be installed away from the policy because of environmental constraints, but to measure a small policy, you should choose a high optical resolution thermometer. The higher the optical resolution, that is, the higher the D:S ratio, the higher the cost of the thermometer.
Determine the wavelength scale
The emissivity and appearance characteristics of the policy data determine the spectral response or wavelength of the thermometer. Regarding high reflectivity alloy data, there is a low or altered emissivity. In the high temperature zone, the best wavelength for measuring metal data is near-infrared, with a wavelength of 0.18-1.0 μm. Other temperature zones are available with 1.6μm, 2.2μm and 3.9μm wavelengths. Because some data is clear at certain wavelengths, infrared energy will penetrate these data, and special wavelengths should be chosen for this data. For example, the internal temperature of the measuring glass should be 10μm, 2.2μm and 3.9μm (the glass to be tested should be very thick, otherwise it will pass through); the internal temperature of the measuring glass should be 5.0μm; the low temperature should be 8-14μm; For example, the polyethylene plastic film is selected to have a wavelength of 3.43 μm, and the polyacetate is selected to have a wavelength of 4.3 μm or 7.9 μm. The thickness exceeds 0.4mm and the wavelength is 8-14μm; if the CO2 in the flame is measured with a narrow band of 4.24-4.3μm, the C0 in the flame is measured with a narrow band of 4.64μm, and the N02 in the flame is measured with a wavelength of 4.47μm.
Determine the moment of response
The echo moment indicates the reaction speed of the infrared thermometer to the measured temperature change, which is defined as the time required to reach 95% of the final reading (only 5% energy required for the two-color colorimetric fiber), and the photodetector, signal processing The circuit is related to the time constant of the visualization system. The new infrared thermometer responds to a time of up to 1ms. This is much faster than the touch temperature measurement method. If the speed of the policy is fast or the speed of heating is measured, the infrared thermometer should be selected to respond quickly. Otherwise, the signal response will not be met, and the measurement accuracy will be lowered. However, not all applications require an infrared thermometer that responds quickly. When there is thermal inertia in the stop or policy hot process, the response time of the thermometer can be relaxed. Therefore, the selection of the infrared thermometer response time should be adapted to the condition of the measured policy.
Trust Through the above introduction, we should be able to choose the products that are suitable for their own use when purchasing the infrared thermometer.