Important elements of purchasing an infrared thermometer

From: Shanghai Zhengqianwang  Date:2018-06-05 18:13:08  Hits:760  Belong to:company news
Non-contact infrared temperature measurement is a mature but dynamic technology that has won the attention of many industries and institutions. It is an essential technology for many temperature measurement applications, especially for industry. If the user fully understands the infrared temperature measurement technology and properly considers all relevant application parameters, as long as the device is carefully installed, the application can usually be successfully performed.
   Careful installation by the user means ensuring that the sensor operates within its specified environmental limits and that adequate measures are taken to keep the optics clean and free of obstacles. When choosing a manufacturer, one factor in the selection process should be the availability of protection and mounting accessories, and the extent to which these accessories can allow rapid sensor removal and replacement for maintenance. If these guidelines are followed, non-contact infrared thermometers will work more reliably than contact thermocouples or resistance thermometers in many cases. With the technology and continuous development, the advancement of non-contact infrared thermometer technology has provided users with various functions and multi-purpose instruments, and expanded the range of infrared products for infrared temperature users.
When selecting the thermometer model, you should first determine the measurement requirements, such as the measured target temperature, the size of the measured target, the measurement distance, the measured target material, the environment in which the target is located (environment temperature, water vapor, strong acid, strong alkali, etc.) Response speed, measurement accuracy, portable or online, power supply, signal output, etc. In the comparison of existing types of thermometers, select the instrument model that can meet the above requirements; among many models that can meet the above requirements Choose the best match in terms of performance, functionality and price. Other options, such as ease of use, maintenance and calibration performance.
    1. First determine the temperature measurement range
    Determine the temperature measurement range: The temperature measurement range is one of the most important performance indicators of the thermometer. Each type of thermometer has its own specific temperature range. The product covers a range of minus 60 ° C to minus 3500 ° C, but you cannot just choose an infrared thermometer model with a wide temperature range. The user must consider the accuracy of the temperature when selecting the temperature range. The repeatability of the temperature should not be too narrow or the temperature range should be too wide. The narrower the temperature measurement range, the higher the resolution of the output signal of the monitored temperature, and the easier the accuracy and reliability can be solved. The temperature measurement range is too wide, which will reduce the temperature measurement accuracy.
2.Secondly determine the material of the measured object
Different types of objects have different emissivities, and the corresponding infrared temperature measurement products are selected according to the emissivity.
The emissivity and surface characteristics of the target material determine the corresponding wavelength of the thermometer's spectrum. For high reflectivity alloy materials, there is a low or varying emissivity. In the high temperature region, the best wavelength for measuring metal materials is near infrared, which can be selected from 0.8 to 1.0 μm. Other temperature zones are available in 1.6μm, 2.2μm and 3.9μm. Since some materials are transparent at a certain wavelength, infrared energy will penetrate these materials, and a special wavelength should be selected for this material.
  For example, the internal temperature of the glass should be 1.0 μm, 2.2 μm, and 3.9 μm (the measured glass must be thick, otherwise it will transmit). The surface temperature of the glass should be 5.0 μm. The low temperature area should be 8 to 14 μm. For example, the measurement of polyethylene plastic film is 3.43μm, polyester is 4.3μm or 7.9μm, and thickness of more than 0.4mm is 8-14μm. For example, a narrow band of 4.64 μm is used to measure CO in the flame, and 4.47 μm is used to measure NO 2 in the flame.
For example, the conventional thermometer produced by Shanghai Zhengqianwang Electric Group is suitable for measuring the temperature of objects and materials that are difficult to access or move. Including paper, thick plastic, rubber, food and organic materials, as well as painted metal and the dirtiest, rusty or greasy surfaces, can be accurately, safely and cleanly measured.
And Shanghai Zhengqianwang Electric's infrared thermometer series for measuring metals is suitable for measurement (casting, sintering, blast furnace continuous casting processing, forging, metal packaging, high temperature heat treatment, hot formed steel panels, vacuum carburizing precision heat treatment, high temperature vacuum Heat treatment, fastener heat treatment, hydrogen embrittlement, hot rolling mill, tube rolling mill, wire rolling mill, galvanized annealing line, aluminum brazing, aluminum processing, aluminum solution, etc.) temperature.
3.Determine the target size
     In order to obtain accurate temperature readings, the distance between the thermometer and the test target must be within a suitable range. The so-called "spot size" is the area of ​​the thermometer's measurement points. The farther you are from the target, the larger the spot size.
     If the size of the target is smaller than the field of view, the background radiant energy will enter the audiovisual branch of the thermometer and interfere with the temperature reading, causing errors. If the target is larger than the field of view of the thermometer, the thermometer will not be affected by the background outside the measurement area. For a colorimeter, its temperature is determined by the ratio of the radiant energy in two independent wavelength bands. Therefore, when the target to be measured is small, not full of the field of view, and there is smoke, dust, or obstruction on the measurement path that attenuates the radiant energy, it will not affect the measurement result. Even in the case of energy attenuation of 95%, the required temperature measurement accuracy can still be guaranteed.
4. Determine the distance coefficient (optical resolution)
    The distance coefficient is determined by D: S, which is the ratio of the distance D between the thermometer probe and the target to the measured target diameter S. The higher the optical resolution, which is to increase the D: S ratio, the higher the cost of the infrared thermometer. If the infrared thermometer must be installed far away from the target due to environmental conditions, and you need to measure a small target, you should choose a thermometer with high optical resolution.
5.Determine the response time
     The response time is defined as the time required to reach 95% of the energy of the last reading. It represents the reaction speed of the infrared thermometer to the measured temperature change. It is related to the time constant of the photodetector, signal processing circuit and display system. The choice of the response time of the infrared thermometer should be adapted to the situation of the target to be measured, and the determination of the response time is mainly based on the speed of the target's movement and the temperature of the target.
    If the target moves fast or measures a fast-heating target, a fast-responding infrared thermometer should be used; otherwise, a sufficient signal response cannot be achieved, which will reduce the measurement accuracy. However, not all applications require fast response infrared thermometers. When there is thermal inertia for stationary or target thermal processes, the response time can be relaxed. For example, the response time of the infrared thermometer produced by Shanghai Zhengqianwang Electric has 5ms, 100ms, 150ms, 300ms, etc.
     6, the infrared thermometer signal output is diversified
     The infrared thermometer has multiple signals and various signal outputs (i.e. 4-20mA, 0-5V, 0-10V, E, K, RS-485 or RS-232
7.Consideration of environmental conditions
     The environmental conditions in which the thermometer is located have a great impact on the measurement results, and should be considered and properly resolved, otherwise it will affect the temperature measurement accuracy and even cause damage. When the ambient temperature is high and there is dust, smoke and steam, accessories such as protective covers, water cooling, air cooling systems, and air purifiers provided by Guangzhou Huahong Automation Equipment Co., Ltd. can be used. These accessories can effectively solve the environmental impact and protect the thermometer to achieve accurate temperature measurement.
     In the case of harsh and complicated environmental conditions, a system with a separate temperature head and display can be selected to facilitate installation and configuration.
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