Does anyone know anything about handheld infrared thermometers?

According to the instructions, it’s also available on the device itself. Instructions for using an infrared thermometer: I. How to choose an infrared thermometer properly 1. Select the range that is most suitable for your application. 2. Provide accurate information regarding the size and material of the object being measured. 3. Understand correctly the optical resolution of the thermometer you have chosen. 4. Take into account the conditions of the environment in which the measurement will be taken. II. How to use an infrared thermometer for temperature measurement? 　　To measure temperature with an infrared thermometer, aim the thermometer at the object whose temperature is to be measured, press the trigger to read the temperature data on the instrument’s LCD, and ensure that the ratio of distance to spot size as well as the field of view are properly set. There are a few important things to keep in mind when using an infrared thermometer: 1. It only measures surface temperature; infrared thermometers cannot measure internal temperatures. 2. Temperature measurement cannot be performed through glass, as glass has very special reflection and transmission properties that prevent accurate infrared temperature readings. However, temperature can be measured through an infrared window. Infrared thermometers should preferably not be used for measuring the temperature of shiny or polished metal surfaces (such as stainless steel, aluminum, etc.). 3. Locate the hot spot: to identify it, the instrument is aimed at the target, and then moves up and down over that target until the hot spot is determined. 4. Pay attention to environmental conditions: steam, dust, smoke, etc. It blocks the optical system of the instrument, affecting accurate temperature measurement. 5. Ambient temperature: If an infrared thermometer is suddenly exposed to an ambient temperature difference of 20 degrees or more, it is allowed 20 minutes to adjust to the new ambient temperature. III. How to ensure the temperature measurement accuracy of an infrared thermometer? 　　The undisputed understanding of infrared technology and its principles is its precise temperature measurement. When measuring temperature with an infrared thermometer, the infrared energy emitted by the object being measured is converted into electrical signals by the optical system of the thermometer at the detector, and the temperature reading corresponding to these signals is displayed. There are several factors that determine the accuracy of temperature measurement; the most important ones are emissivity, field of view, distance to the light spot, and the position of the light spot. Emissivity: All objects reflect, transmit, and emit energy, but it is only the energy emitted that can indicate an object’s temperature. When an infrared thermometer measures surface temperature, it can detect all three types of energy. Therefore, all infrared thermometers must be adjusted to read only the emitted energy. Measurement errors are usually caused by infrared energy reflected from other light sources. Some infrared thermometers allow the emissivity to be changed, and the emissivity values for various materials can be found in published emissivity tables. Other instruments have a fixed emissivity preset to 0.95. For the surface temperatures of most organic materials, paints, or oxidized surfaces, this emissivity value requires compensation by applying tape or flat black paint to the surface being measured. When the tape or paint reaches the same temperature as the base material, measuring the temperature of its surface gives its true temperature. The ratio of distance to spot size: The optical system of an infrared thermometer collects energy from a circular measurement spot and focuses it on the detector. Optical resolution is defined as the ratio of the distance from the infrared thermometer to the object to the size of the measured spot (D:S). The larger the ratio, the better the resolution of the infrared thermometer, and the smaller the size of the light spot being measured. Laser aiming is used only to assist in aiming at the measurement point. The latest improvement in infrared optics is the addition of a near-focal feature, which enables accurate measurement of small target areas and also prevents the influence of background temperatures. Field of view: Ensure that the target is larger than the size of the light spot generated by the infrared thermometer; the smaller the target, the closer one needs to be to it. When precision is particularly important, ensure that the target is at least 2 times the size of the spot. This post was last edited by dongliangsir on 2009-2-23 20:50.]

The explanation on the 2nd floor is very comprehensive. Our company uses Fluke infrared thermometers, and their accuracy meets the required standards. Used according to the instructions, and it has quite high accuracy.

It is suitable for use in applications where high precision is not required, to determine whether the equipment is operating properly; it is not appropriate for measuring data from tests and experiments, such as the temperature of the seal in pump motors, the operating temperature of bearings, the temperature of steam pipes, or the temperature of cooling water. There is also a rough comparison between the temperature of the reactor and the temperature indicated by the thermometer. Keep the distance as short as possible when using it; in practice, it’s best to determine the temperature loss of your equipment’s materials and add that value as well.

Infrared thermometers still need to be calibrated; sometimes there are errors, but they’re not very large!

Our factory is also using this mid-infrared thermometer, and it’s really great! :handshake

Our factory mainly uses it for a rough estimation of the temperature of blowers, motor housings, or pipes. It’s convenient to shoot with a gun. At the same time, it is best to calibrate the infrared gun once a year. Sometimes it seems to work well, but in fact the error is already quite large.

I’ve used it too; it measures the average temperature of the area in question. When the distance is greater, the area that is measured appears larger. It depends on your needs – you must ensure that the device is aimed at the area you want to measure, otherwise the errors can be significant, especially at greater distances. Be particularly careful in such cases

Infrared temperature measurement cannot achieve very high precision; it is mainly used for measuring the temperature of devices that cannot be touched or for which it is inconvenient to make contact.

First, understand the emissivity data of the object being measured. If you’re not sure, you can stick a piece of black tape on the object. Black surfaces generally have a high emissivity, exceeding 0.9, which is similar to the emissivity set for ordinary infrared thermometers; as a result, the error is very small. The distance from the temperature generally has little impact ； The effect of measuring reflective surfaces is quite significant.

The error in infrared thermometers is greatly influenced by human factors: one should not measure low-temperature objects right after measuring high-temperature ones. It is better to press the thermometer several times in a low-temperature environment or elsewhere indoors after measuring the high-temperature object, waiting until the temperature returns to room temperature before measuring high- or low-temperature equipment, in order to obtain more accurate results.

As is well known, temperature is one of the most important parameters in heating, gas supply, ventilation, and air conditioning systems. Especially in thermal measurement processes, the accuracy of temperature is often the key factor determining the success or failure of an experiment. Therefore, a high-precision temperature measuring instrument is essential in engineering. Therefore, this article provides an introduction to the principles and applications of infrared thermometers among temperature measurement tools. 1. The theoretical principle of infrared temperature measurement: In nature, when an object’s temperature is above absolute zero, its internal thermal motion causes it to continuously emit electromagnetic waves, including infrared rays with wavelengths ranging from 0.75µm to 100µm. Its most notable characteristic is that, at a given temperature and wavelength, the radiant energy emitted by an object reaches a maximum value; such a substance is called a black body, and its reflectivity is set to 1. Other substances have a reflectivity of less than 1 and are referred to as gray bodies. The spectral radiant power P(λT) of a black body obeys Planck’s law in relation to the absolute temperature T. It indicates that at absolute temperature T, the radiant power per unit area of a black body at wavelength λ is P(λT). Based on this relationship, the curve shown in Figure 1 can be obtained. It can be seen from the figure that: (1) as the temperature increases, the object’s radiant energy becomes stronger. This is the starting point of infrared radiation theory, as well as the basis for the design of single-band infrared thermometers. (2) As the temperature increases, the peak of radiation shifts toward shorter wavelengths (to the left), and this follows Wien’s displacement law: the wavelength at the peak is inversely proportional to the absolute temperature T. The dashed line represents the lines connecting the peaks. This formula explains why high-temperature thermometers operate primarily in the short-wave range, while low-temperature thermometers operate primarily in the long-wave range. (3) The rate of change of radiation energy with temperature is greater at short wavelengths than at long wavelengths; therefore, thermometers operating at short wavelengths have a higher relative signal-to-noise ratio (higher sensitivity) and better resistance to interference. Thermometers should preferably be chosen to operate at the peak wavelength, especially in cases of low temperatures and small targets, as this is particularly important. Second, the principle of infrared thermometers. An infrared thermometer consists of an optical system, a photodetector, a signal amplifier, as well as components for signal processing and display/output. The radiation from the object under test and the feedback source is modulated by a modulator before being fed into the infrared detector. The difference between the two signals is amplified by an inverse amplifier, which in turn controls the temperature of the feedback source so that the spectral radiance of the feedback source matches that of the object. The display indicates the brightness temperature of the object being measured. Three, the performance parameters and functions of infrared thermometers include the temperature measurement range, display resolution, accuracy, operating temperature range, repeatability, relative humidity, response time, power supply, response spectrum, size, maximum value display, weight, emissivity, etc. 1. Determining the temperature measurement range: The temperature measurement range is one of the most important performance parameters of a thermometer. Each type of thermometer has its own specific temperature measurement range. Therefore, the temperature range to be measured for the user must be determined accurately and comprehensively, neither too narrow nor too wide. According to the law of blackbody radiation, the change in radiant energy caused by temperature in the short-wavelength region of the spectrum will exceed the change in radiant energy caused by emissivity errors. 2. Determine the target size: Infrared thermometers can be classified into monochromatic thermometers and dichromatic thermometers (radiance colorimetric thermometers) based on their working principle. For a monochromatic thermometer, when taking temperature measurements, the area of the object being measured should fill the thermometer’s field of view. It is recommended that the size of the target being measured be more than 50% of the field of view. If the target size is smaller than the field of view, the background radiation energy will enter the sensor’s visual path and interfere with the temperature measurement, resulting in errors. Conversely, if the target is larger than the thermometer’s field of view, the thermometer will not be affected by the background outside the measurement area. For a two-color thermometer, the temperature is determined by the ratio of the radiant energy in two separate wavelength bands. Therefore, when the target under measurement is very small and does not fill the field of view, or when there is smoke, dust, or obstacles in the measurement path that cause attenuation of the radiant energy, these factors do not have a significant impact on the measurement results. For small targets that are in motion or vibrating, a dual-color thermometer is the best choice. This is because light has a small diameter and flexibility, allowing it to transmit optical radiation energy through curved, obstructed, and folded pathways. 3. Determine the distance factor (optical resolution): The distance factor is determined by the ratio D:S, that is, the ratio of the distance D between the thermometer probe and the target to the diameter of the target being measured. If, due to environmental constraints, the temperature sensor must be installed at a distance from the target and it is necessary to measure a small target, a temperature sensor with high optical resolution should be chosen. The higher the optical resolution, that is, the greater the D:S ratio, the higher the cost of the temperature sensor. If the thermometer is far from the target and the target is small, a thermometer with a high distance coefficient should be chosen. For a temperature sensor with a fixed focal length, the spot size is smallest at the focus of the optical system; it increases both near and far from the focus. There are two distance coefficients. 4. Determine the wavelength range: The emissivity and surface properties of the target material determine the corresponding wavelength in the spectrum used by the thermometer. For highly reflective alloy materials, the emissivity is low or variable. In high-temperature areas, the optimal wavelength for measuring metal materials is in the near-infrared range, with 0.8–1.0 μm being suitable choices. For other temperature ranges, 1.6μm, 2.2μm, and 3.9μm can be used. Since some materials are transparent at certain wavelengths, infrared energy can penetrate them; therefore, a specific wavelength should be chosen for such materials. 5. Determine the response time: The response time indicates the speed at which an infrared thermometer reacts to changes in the temperature being measured. It is defined as the time required for 95% of the energy to reach the final reading, and it is related to the time constants of the photodetector, the signal processing circuitry, and the display system. If the target is moving at high speed or when measuring a target that heats up rapidly, a fast-response infrared thermometer should be used; otherwise, an adequate signal response will not be achieved, which will reduce the measurement accuracy. However, not all applications require infrared thermometers with fast response times. For stationary conditions or when the target thermal process has thermal inertia, the response time requirement for the temperature sensor can be relaxed. 6. Signal processing functions: Given the differences between discrete processes (such as part manufacturing) and continuous processes, infrared thermometers are required to have multiple signal processing functions available for selection, such as peak holding, valley holding, and average value calculation. When measuring the temperature of bottles on a conveyor belt, peak holding is used, and the resulting temperature signal is sent to the controller. Otherwise, the thermometer will read the lower temperature value between the bottles. If peak holding is used, set the thermometer’s response time to be slightly longer than the interval between bottles, so that at least one bottle is always under measurement. 7. Consideration of environmental conditions: The environmental conditions in which the thermometer is located have a significant impact on the measurement results; these conditions must be taken into account and addressed appropriately, otherwise it may affect the accuracy of temperature measurement or even cause damage to the thermometer. When the ambient temperature is high and there is dust, smoke, and steam present, accessories such as the protective cover provided by the manufacturer, water cooling systems, air cooling systems, and air blowers can be used. These attachments can effectively address environmental impacts and protect the thermometer, ensuring accurate temperature measurement. When determining the attachments, standardized services should be sought as much as possible to reduce installation costs. 8. Calibration of infrared radiation thermometers: Infrared thermometers must be calibrated in order to accurately display the temperature of the object being measured. If the thermometer used experiences temperature measurement errors during use, it must be returned to the manufacturer or repair center for recalibration. IV. Main factors affecting infrared thermometers 1. Relationship between the size of the object being measured and the measurement distance: At different distances, the effective diameter D of the object that can be measured varies; therefore, when measuring small objects, attention must be paid to the distance from the object. The distance coefficient K of an infrared thermometer is defined as the ratio of the distance L from the object being measured to its diameter D, that is, K = L/D. 2. Selecting the emissivity of the material being measured: Infrared thermometers are generally calibrated based on a black body (emissivity ε = 1.00), but in reality, the emissivity of materials is always less than 1.00. Therefore, when it is necessary to measure the true temperature of the target, an emissivity value must be set. The emissivity of materials can be found in \"Data on the Emissivity of Objects in Radiometric Temperature Measurement.\" 3. Measurement of targets in a bright light background: If the target to be measured is surrounded by bright background light (especially when exposed directly to sunlight or strong lamps), the accuracy of the measurement will be affected. Therefore, an object can be used to block the direct light on the target in order to eliminate the interference from the background light. 4. Measurement of small targets: (1) The thermometer should be mounted on a tripod (an optional accessory). (2) Precise focusing is required: align the small black dot in the eyepiece with the target (the target should fill the entire small black dot); adjust the lens back and forth while slightly moving the eyes. If there is no relative movement between the small black dots being measured, then focusing is complete. 5. Temperature output functions: (1) Digital signal output – RS232, RS485, allowing for remote transmission of temperature signals. (2) Analog signal output – 0～5V, 1～5V, 0～10V, 0/4～20 milliamps; these signals can be used in closed-loop control systems. (3) High alarm, low alarm – During the production process, it is necessary to keep the temperature within a certain range; high and low alarm values can be set accordingly. High alarm: When the high alarm setting is enabled, if the temperature exceeds the high alarm value, the corresponding LED light flashes, the buzzer sounds, and the AH normally open relay is activated. V. Characteristics of infrared thermometers: 1. Non-contact measurement: It does not require contact with the interior or surface of the temperature field being measured; as a result, it does not interfere with the state of that temperature field, and the thermometer itself is not damaged by the temperature field. 2. Wide measurement range: Since it is a non-contact temperature measurement method, the thermometer does not operate in extremely high or low temperature environments, but rather under normal temperatures or within the conditions permitted by the thermometer. Under normal circumstances, it can measure from negative dozens of degrees to over 3,000 degrees. 3. Fast temperature measurement speed: that is, a quick response time. It can maintain a constant temperature in a short time as long as it receives the target’s infrared radiation. 4. High accuracy: Infrared temperature measurement does not disrupt the object’s original temperature distribution like contact-based temperature measurement, thus ensuring high precision. 5. High sensitivity: Even a slight change in the object’s temperature results in a significant change in radiation energy, making it easy to detect. It can perform temperature measurements of subtle temperature fields and temperature distribution measurements, as well as temperature measurements of moving or rotating objects. It is safe to use and has a long service life. 6. Disadvantages of infrared thermometers: 1. They are susceptible to environmental factors such as ambient temperature and dust in the air. 2. Their measurement readings are greatly affected by shiny or polished metal surfaces. 3. They can only measure the surface temperature of an object, making it difficult to determine the temperature inside the object or when there are obstacles present. 7. Precautions for using infrared thermometers: (1) It is necessary to accurately determine the emissivity of the object being measured; (2) Avoid the influence of hot objects in the surrounding environment; (3) For transparent materials, the ambient temperature should be lower than that of the object being measured; (4) The thermometer must be aligned vertically with the surface of the object being measured, with the angle never exceeding 30 degrees under any circumstances; (5) They cannot be used to measure the temperature of shiny or polished metal surfaces, nor can they be used to take measurements through glass; (6) Choose the appropriate focusing factor, and ensure that the diameter of the target fills the field of view; (7) If the infrared thermometer is suddenly exposed to an ambient temperature difference of 20 degrees Celsius or more, the measurement results will be inaccurate; wait until the temperature reaches equilibrium before taking the measurement value. 8. Improvement solutions: Since ordinary infrared thermometers can only measure the temperature of the outside of an object, making it difficult to determine the temperature inside the object or when there are obstacles present, a section of optical fiber can be added to their sensing head, along with a lens having a narrow field of view at its front end. In this way, the radiation emitted by the object being measured can pass through the lens and into the optical fiber. It travels through the optical fiber via multiple reflections before reaching the detector. Since optical fibers can bend freely, allowing the radiation energy to be directed as needed, this solves the problem of measuring temperatures inside objects; it is possible to measure the temperature in areas blocked by obstacles. For example, the temperature of plastic is measured inside plastic extruders; in turbines, the highest and average temperatures of the rotating blades are measured through the gaps in the stationary blades, and multiple probes can be used for cyclic monitoring. 1. Principle of fiber optic infrared temperature measurement: The principle of light transmission in fibers is the phenomenon of total internal reflection of light in different media. When light travels from a denser optical medium to a less dense one, it is completely reflected back into the denser optical medium at the boundary. Light travels in a zigzag pattern within the fiber core, without leaking out. 2. Structural diagram: The infrared radiation from the object being measured is focused by the lens of the infrared probe onto the front end of the optical fiber. The infrared energy, after being transmitted through the optical fiber and filtered by an infrared filter, is detected by the infrared detector and converted into corresponding electrical signals. These electrical signals are amplified and linearized by electronic circuits before being output in a standard signal format. 3. Advantages of fiber optic temperature measurement: (1) Fiber optic probes can withstand high temperatures, allowing them to be used in environments with high temperatures. (2) By transmitting infrared energy through optical fibers, the infrared probe is separated from the electronic processing module, thereby minimizing the impact of environmental factors on the signal processing unit. (3) The fiber optic probe transmits infrared radiation heat energy signals without being affected by electromagnetic fields at all, making it particularly suitable for use in environments with strong electromagnetic fields such as medium- and high-frequency induction heating equipment. (4) It can bend freely, allowing for the free conversion of radiant energy; it can also be used to measure temperatures in areas blocked by obstacles

I’ve used it, but there are errors. It was borrowed from another department in the unit. Thank you to everyone above for the introductions.

In our unit, the plastic at the infrared emission part has been distorted due to high-temperature testing; the temperatures measured are only for rough reference.

Thank you for the reply from above; I would like to purchase an infrared thermometer with a measurement range of -20 to 280 degrees. Measurement distance: 5cm~2m. The surface temperature of the object under test is mainly that of stainless steel or carbon steel (silver-painted) pipes. The error is required to be within plus or minus one degree. Could that person recommend a model for me? Detailed instructions would be even better, thank you!

The Japanese products we use are unavoidable, but they are indeed good with low error rates.

Infrared thermometers all have errors; what’s important is to take multiple measurements in order to identify patterns

If you want to know the accuracy of your handheld infrared thermometer, the manual will provide information on that. Of course, a dual-color model has greater resistance to interference than a single-color one. The accuracy of measurements also depends greatly on whether you know how to set the parameters and operate the device correctly. Different materials have different emissivity values, so it’s important to set this parameter correctly. Additionally, check the calibration records of your handheld device to see what the error level is.