Unlike the standard contact thermometers, infrared thermometers measure reflected light by objects at specified wavelengths. They are used in a wide range of environments and industries to measure surface temperatures quickly. Their efficiency in efficiently detecting potential errors in electrical circuits, building systems, and mechanical equipment, helps avert catastrophes.
Making precise and accurate temperature measurements play a key role in the success of many businesses like manufacturing. This underlines the importance of checking the accuracy of your infrared thermometer. The best way to go about this is by checking the accuracy of the thermometer to make sure you get the right temperature measurements.
This article will outline everything you need to know on how to check the accuracy of your infrared thermometer, and the factors that affect its accuracy.
Accuracy of Infrared Thermometer
1. Use a Blackbody Calibrator
Theoretically, blackbody calibrators are “perfect emitters,” which means that they emit maximum infrared energy at a given temperature. Besides, they radiate the same radiation intensity in every direction. That is the reason why they provide a strong calibration basis when checking the accuracy of infrared thermometers.
With the use of an accurate pyrometer, the blackbody temperature is measured, and because its emissivity is known, it offers accurate calibration. The majority of manufacturers use this method to calibrate their pyrometers and IR thermometers. However, the downside with this accuracy checking method is that blackbody calibrators are expensive and a reserve of the big companies.
2. Use Accurate Pyrometers
Accurate pyrometers record accurate temperature measurements of an area or object. To check the accuracy of your thermometer, you first need to measure and record the temperature of an area or object using an accurate pyrometer. You then measure the exact area using your infrared thermometer and compare measurements. If you find that the two measurements are not corresponding, that means your thermometer is not accurate and will need to be calibrated to match the accurate pyrometer.
When using this method, you must ensure that the pyrometer you are using is accurate; if you have doubts about its accuracy, using two pyrometers can help. Besides, you should measure the temperature of the exact area with the exact thermal energy to ensure accuracy. Different areas or objects will most likely than not record different temperature measurements.
3. Use Thermocouple
A thermocouple is an instrument consisting of different metal wires that are welded at a junction. Changes in temperature make the junction to create a voltage, after which thermocouple tables are used to calculate temperature measurements and interpret voltage.
In this case, an object’s temperature is measured using the accurate thermocouple and recorded, after which the thermometer is used to measure the same object. Their measurements are then compared, and if they do not match, the thermometer is calibrated to rhyme with that of the thermocouple. When using this method of accuracy check, you must measure the same area of the object to ensure accuracy.
It is important to note that thermocouples are not 100% accurate as they wear and tear quite often. However, they come in different varieties, and most often than not, the costly ones tend to have high accuracy. You need to first confirm the accuracy of the thermocouple before using it to base your measurements for accuracy purposes.
4. Ice Water Test
If you do not have a thermocouple, pyrometer, or blackbody calibrator, you can use the ice water test. You have to fill your glass with ice and fill it with water to fill the ice gaps. Let the glass settle for some time preferably two minutes, after which you stir its contents until they are uniform.
Hold your IR thermometer directly on top of the glass at about 3 inches and ensure the thermometer lens is placed at 90 degrees above the glass. Ensure that the thermometer lens is solely aimed at the ice and water to avoid a view of the walls of the grass of the background, which will affect the measurements. If your IR thermometer is reliable and accurate, and you correctly follow these steps, it should record 32.0 degrees.
5. Use Infrared Comparator Cup
The infrared comparator cup allows for a comparison of its accuracy and that of the IR thermometer without using ice and water temperatures. The aluminum cup is made of matte black solid coating and a stable flat surface. Its walls help to shield air currents found in the room from its surface which could affect the accuracy test, while the mass at its base is meant to provide temperature stability.
The reference thermometer is inserted into the cup and allowed to settle for a few minutes for stability. The infrared thermometer is then pointed at the object inside the infrared comparator cup with the same care outlined in the ice water test. If the IR thermometer is accurate, its readings must match with the reference thermometer’s readings.
6. Use a Surface Probe
Another instrument that you can use to check the accuracy of your IR thermometer is the surface probe. Just take and record the surface temperature measurements of the testing object using an accurate surface probe. When taking these measurements, you must ensure that the environment temperature around the objects is stable.
After you have made sure that your IR thermometer readings are stable and you have recorded them, point it to the object from a few centimeters away. Ensure that you point it at the exact spot that you pointed your surface probe and record the readings. If the two readings don’t match, your thermometer is not accurate, and you will need to adjust its emissivity.
Instructions to follow when conducting IR thermometer accuracy test
Infrared thermometer accuracy tests require one to have a stable surface whose temperatures are known and follow instructions. Outlined below are some of the simple instructions that will help you crack the accuracy test.
- The IR thermometer must be allowed to settle for a few minutes in the room where the tests are being done. This is meant to allow the thermometer to adjust to the room temperatures and thus increase its accuracy. For instance, in case you have removed it from a chiller, you must give it time to settle for about 15 – 20 minutes before conducting any tests.
- Ensure your IR thermometer’s lenses are clean before conducting any accuracy tests. In case it has grime, condensation, or debris, it might give misleading measurements. However, you must trend carefully when cleaning it to avoid scratching it or damaging the sensor. The best way of cleaning your thermometer’s lens is by using soft cotton dipped in alcohol.
Clean the lens first and then the body later to avoid causing any damage to them. After cleaning the lens, allow it to dry before use and avoid submerging any of the thermometer’s parts in the water when cleaning, as it can cause damage.
- If conducting the IR thermometer accuracy tests using other instruments like thermocouples, pyrometers, blackbody calibrators, or infrared comparator cup, among others, you must confirm their accuracy first. It would not make any sense to base your accuracy tests on faulty instruments, which will only give you wrong measurements.
- Consider your thermometer’s field of view, which is the distance to target ratio, because it affects its readings. If you falter on the field of view of your thermometer, it will pick up the background of the object and thus give misleading measurements. Each thermometer has its distance to the target ratio indicated on them or in their manual which means all you need to do is obey them.
- Avoid conducting accuracy tests in dusty and steamy rooms. Dust and steam affect the normal functioning of IR thermometers thus recording faulty measurements. If the room is dusty and steamy, you can change the venue and conduct the test in a conducive room.
- Set your thermometer’s settings at 0.95 to 0.97 before conducting any accuracy test. Setting the emissivity of your thermometer enables it to give you the correct readings. Some of them come with factory-set emissivity settings, which are fixed. Emissivity is the measure of an object’s ability to emit infrared energy.
Determinants of Your IR Thermometer Accuracy
Your IR thermometer’s accuracy is determined by a host of factors that you should not overlook while conducting any test. These factors ensure that you get the accurate measurements that you need, as outlined below.
Distance to target Ratio
The distance to the target ratio put is the size of the target area being measured by the thermometer with its distance. This ratio plays a key role in determining the accuracy of the temperature measurements. If the distance to the target ratio of your thermometer is 12:1, this means that when the thermometer is 12 cm away from the object, its diameter is 1cm.
Therefore, if you increase the distance to 13cm, the thermometer will record the temperature of the object plus its background, thus giving false distorting measurements. Distance to the target ratio is displayed on the thermometer and its manual. You must obey your thermometer’s distance to the target ratio for accurate temperature measurements.
Field of view
IR thermometer uses a laser to record the energy emitted by objects, which determines the surface temperature of an object. Therefore, laser guides you on the area to test as it is aimed below the testing area. Most of the thermometers available like IRFS, IR-Gun, IRK, or IRT have their lasers located below their lens.
To get accurate measurements, you must aim the lasers directly to the test area at an angle of 90 degrees. A simple mistake in the position of the laser will give you the wrong measurements. Weed through your thermometer to find the location of your laser so that you can correctly position your field of view.
Every IR thermometer has emissivity settings responsible for recording the maximum amount of energy that objects emit. Some are manufactured with fixed factory set settings, while others have adjustable emissivity settings. For optimum performance, the ideal emissivity settings of an accurate IR thermometer should be 0.95 up to 0.97.
Objects with high or low emissivity levels either reflect or absorb infrared energy, thus affecting the temperature measurements. When measuring the temperature of shiny objects, you must adjust the emissivity settings on your thermometer to record accurate measurements. Besides, you could rap them with non-reflective tape or apply flat paint to record perfect measurements.
The location that you carry out measurements using the infrared thermometer can affect accuracy. For instance, carrying out measurements in steamy or dusty surroundings deflects infrared energy emitted by objects before they can reach the thermometer laser and lens, thus recording faulty measurements.
Also, a dirty or fogged lens could impair the ability of the thermometer to record the energy needed to make measurements. This is the reason why you are discouraged against using the dirty lens and taking measurements in locations filled with dust and steam.
Whenever an IR thermometer is transferred to surroundings with different temperatures, they suffer temperature shock. This, in turn, forces them to record faulty measurements. That is the reason why it is important to allow your thermometer to settle for about 15 to 20 minutes after taking it to warmer or colder surroundings. This allows them to acclimatize with the surroundings thus increasing their accuracy.
Infrared thermometers offer an excellent combination of convenience, speed, and accuracy. Whether you want to measure the temperature of electrical systems, grill surfaces, and duct, among others. They are, therefore, the perfect replacement to standard thermometers, which cannot simply do the work. However, the secret to using them effectively lies in using them correctly by following the laid down instructions as outlined above.
Besides, it is important to ensure that they are giving accurate measurements so that you can make informed decisions. You can only achieve this by carrying out accuracy tests and following their manual instructions. If you follow the accuracy tests above, they will help you to increase the accuracy of your measurements.