Pyrometers are used throughout industry to provide accurate and dependable non-contact measurement of temperature. Due to their suitability for measuring a wide range of materials and ability to measure to very high temperatures, they are used in many process-critical temperature measurement applications. Fortunately, pyrometers are very reliable and will require very little maintenance to keep them operating correctly.
In this article, we discuss common pyrometer issues and how to address them, and how to maintain and calibrate pyrometers to ensure optimum performance and reliability.
Has Your Pyrometer Got Dirty Optics?
Pyrometers are optical devices and they require a clear view of the object that is being measured. As with any optics over time, the lens can be contaminated with dust, dirt, oil or other contaminants. When these contaminants build up, it will start to affect the performance of the pyrometer, as the amount of infrared light that will be received by the internal detector will be attenuated.
To address this issue, clean the lens using a lint-free cloth and an alcohol-based optic cleaning fluid. A cotton bud can be helpful to clean right up to the edges of the lens. For applications in dirty or dusty environments, it is recommended that an air purge is specified to reduce the cleaning interval. It should be noted that dual-colour (or ratio) pyrometers are much more tolerant to the build-up of dirt on the optics and are a better choice when there are fumes, smoke, steam or dust between the pyrometer and the object being measured. Due to the underlying ratio principle, these types of pyrometers will continue to measure accurately even when the optics or air is contaminated.
Explore Our Range of Impac Pyrometers at LIMAB UK
Has Your Pyrometer Overheated?
As pyrometers are used to measure the temperature of objects, they are often located near sources of heat and, therefore, can be exposed to raised ambient temperatures. Like any electronic device, the pyrometer has a safe operating temperature. Typically, this is between 0 and 60 or 70°C depending on the pyrometer model. If the upper-temperature limit is exceeded, the accuracy can drift and even permanently damage the electronic components.
Most Impac® pyrometers have an internal temperature sensor. By connecting using the service software provided, it is possible to read both the current and maximum temperature internal temperature. If the maximum internal temperature has exceeded the upper limit, we would recommend that the pyrometer is returned to LIMAB UK for inspection and calibration. It should be noted that for installation in hot ambient environments, air or water-cooling cooling accessories are available to maintain the pyrometer at a safe temperature.
Check Your Pyrometer Alignment with the Object
Correct alignment of the pyrometer with the target is critical for accurate temperature measurement. When the pyrometer was originally installed, it would have been carefully aligned by the installation technician to measure the temperature of an object at a specific location. We have seen many cases where the pyrometer has been accidentally knocked or moved so that it is no longer viewing the correct part of the object. This results in an apparent temperature measurement error, but when investigated, the error is due to the pyrometer measuring the object at the wrong location. This problem is more acute when measuring very small objects, as the measuring spot must be precisely aligned with the object for correct temperature measurement.
Therefore, it is good practice to verify that the alignment is correct as originally intended. Most Impac® pyrometers are equipped with a laser sighting spot or through lens sighting optics to allow precise alignment. It should be noted that dual-colour pyrometers are better suited for measuring very small objects, as the spot does not need to be completely filled by the hot object; for example, when measuring a moving wire or hot pouring stream.
In the case of single-colour pyrometers, the object must be bigger than the measuring spot or a temperature measurement error will occur. A dual-colour pyrometer will continue to correctly measure the temperature if part of the spot is not on the object.
The Importance of Regular Calibration for Pyrometers
How Often Should an Infrared Pyrometer Be Calibrated?
The frequency of calibration depends on how critical the measurement is in the process. The more critical and precise the measurement, the shorter the calibration interval. It is important to refer to your company’s internal quality standards, which will specify the calibration interval. In general, if it is not specified, it is common practice for infrared pyrometers to be calibrated against a verified blackbody temperature reference source once a year.
How Do I Calibrate My Pyrometer?
To verify a pyrometer is measuring temperature accurately, it must be calibrated using a blackbody temperature source. The blackbody’s actual temperature is confirmed using a calibrated transfer standard pyrometer (TSP), which has a known uncertainty of measurement. The pyrometer to be calibrated then measures the temperature of the blackbody, allowing for accuracy to be established at that specific temperature.
Typically, it is standard practice to calibrate at least two or three temperature points that are representative of the pyrometer’s intended temperature range. Once the calibration is completed, a calibration certificate can be issued.
As most companies do not have blackbody or TSP, the calibration of the pyrometer will need to be done by the pyrometer manufacturer or third-party certified calibration house.
If you require your pyrometers to be calibrated, it can be returned to LIMAB UK. Please contact one of our product specialists using our contact form.
Regular maintenance and calibration of your pyrometer can ensure accurate temperature measurements, increase the pyrometer’s lifespan and reduce downtime. If you have any questions or concerns about your pyrometer’s performance or require it to be calibrated to national standards, consult with one of our product specialists using our contact form.
Learn more about LIMAB UK’s range of non-contact pyrometer calibration devices on our temperature measurement page.
