FOT

【 guide Is also a temperature measurement, why you uncertainty?

by:FOT     2020-11-24
The use of temperature measurement based on sensors, usually divided into contact temperature test contactless temperature measurement in two ways. Portable infrared thermometer as a non-contact temperature measurement products, small blessing believe that everybody is not strange. Both in the preventive maintenance of electrical equipment, production line quality control, or restaurant food hygiene and safety, a lot of life, work, production temperature scenario, because the non-contact infrared thermometer, fast response characteristics, it has become the important temperature measuring tool. But sometimes you may encounter questions such as why choose thermometer precision obviously enough but the temperature of the measured values or deviation so big? Today small blessing for everyone finishing some common problems of infrared thermometer collection quickly up 1 should how far is the distance from the target temperature? Measurement is the temperature of the laser spot? Measuring the relationship between target size and temperature measuring distance D: S infrared thermometer for temperature measurement, temperature is measured by the laser point as the center of a circular view within the scope of the average temperature measurement. Target area to be tested should be full of the circular measurement field. If the target size is less than the field of view, the background of the surrounding temperature or other heat source will be included in the measurement field, the interference temperature readings, caused the error. So general recommendation measured target size by more than 50% of the field size as well. By the following diagram is instantly clear there may be someone will ask, that how to know the measurement field is how much? Size of infrared thermometer measurement field, it is as the thermometer probe and the changes in distance, then you can imagine thermometer for a flashlight, a circular spot for measuring field, namely the farther the distance light, the greater the distance between the closer flare is smaller. At work we need to accurately calculate the diameter of the field measurement, to determine when measuring different sizes of target, we should how far away, to help us more accurate temperature measurement. Infrared thermometer is an important parameter, distance coefficient ratio D: S, it is defined as: the distance of the measured target D and the ratio of the diameter measurement field S. For example, an D: S of 10:1, infrared thermometer when and target being measured at 1 m distance D temperature measurement, temperature field of S to 10 cm in diameter. When the measured target should be not less than 10 cm. 2 why do some objects measured values deviation? Choose emissivity of object to be tested when we use the infrared thermometer, whether to accurately select the emissivity of the object to be tested, will also affect temperature numerical accuracy. Infrared thermometer factory default emissivity value of 0. 95, so we need to first determine corresponding emissivity of the object under test, and then adjust the thermometer to the corresponding emissivity values, start temperature measurement. The emissivity of different substances are not identical, numerical value between 0 - 1, material of dielectric constant, surface roughness, temperature, wavelength and direction of observation conditions will affect emissivity. When measured target emissivity is bad judgement, there are two proposals: 1. If the measured target allows, can be in surface paste black electrical tape or daub thermal conductive silicone, these two kinds of material emissivity of 0. 95, when the temperature balance, measuring paste adhesive tape or thermal conductive silicone area. 2. Contact thermometer is used to measure the actual temperature, at the same time, constantly adjust the emittance of infrared thermometer, until the value is the same as the actual temperature infrared thermometer or close to, the emissivity of the measured target at this time the correct firing rate. ( Finally, the paper include common material emissivity reference table for your reference) Note 1 3 other measurements. Infrared thermometer measuring surface temperature only, can't measure the internal temperature. 2. If the thermometer suddenly exposed to the environment temperature is 20 ℃ or higher, instrument need 20 minutes to adjust to the new environment temperature. 3. If the measured target has a light background light ( Especially under direct sunlight or strong light) Around, or have a thorough knowledge of the other heat source, the measurement accuracy will be affected, so can keep out measures should be taken to prevent strong light of direct target to eliminate ambient light interference. 4. If the target is translucent materials, such as plastic, glass, etc. , shall ensure that the background is uniform and lower than the temperature of the target. 5. If the emissivity of target is lower than 0. 90, should try to keep when temperature measuring instrument and the measured surface vertical measurement. 6. Steam, such as dust, smoke, it blocks the optical system and affect the temperature measurement instrument. In order to avoid damage to the infrared thermometer, please first use compressed air to remove large particles and dust, then wipe with a cloth. Use clean slightly wet cloth gently wipe the thermometer fuselage. If necessary, can add a small amount of mild soap with water to go into the solution of wet the cloth. Common emissivity of form
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