Calibration functions for temperature controllers and process controllers are not frequently used, but their proper application can significantly improve system efficiency and product quality. This article introduces the basics of input calibration and some of its advantages, providing useful guidance for those who have never performed input calibration before, and revealing its deeper benefits to the system.
Why is it necessary to calibrate the controller?
West Control Solutions calibrates its controllers at the factory to achieve the accuracy specified in the product specifications. Factory calibration treats the controller as a standalone device without considering the overall system factors in which it is used. Many external factors affect the overall system accuracy, such as sensor accuracy and positioning; additionally, cable type and length can introduce errors. By using the controller's input calibration function, you can eliminate these errors and achieve the desired overall system accuracy.
If the controller is not calibrated, even a small error can severely impact output quality. For example, the aerospace industry has extremely high safety requirements, and high precision is crucial for achieving safety. Similarly, the success of manufacturing depends on whether products meet quality control requirements. Aircraft manufacturers, in order to obtain Nadcap (National Aeronautics and Defense Authorization Program) certification, must establish comprehensive quality systems, including thorough process guidelines and complete records for all production batches (including time and temperature data). To ensure aircraft quality, manufacturers also regularly conduct system accuracy tests to ensure the system is correctly calibrated within permissible parameter ranges. The U.S. Food and Drug Administration requires similar system accuracy testing for the pharmaceutical industry, while in the life sciences industry, a narrow temperature range is critical to ensuring experiments and tests are conducted under optimal temperature conditions. On the other hand, in some processes, manufacturers' high requirements for temperature tolerance are not based on standard specifications but rather on improving process efficiency.
No manufacturer wants to go through multiple trials before producing a qualified product, or to have to stop production due to poor output quality. Ensuring system accuracy will effectively prevent these situations from happening.
How to perform input calibration?
In process equipment, sensors are installed as close to the product as possible, while the controller displays the sensor measurements: the sensor provides an analog signal through its input, and the controller then converts this analog signal into a digital signal for display. During controller calibration, the displayed value is compared to a correctly calibrated temperature measurement to determine the error.
There are two methods for calibrating temperature sensors: single-point calibration, also known as zero-point drift calibration, and two-point calibration. Single-point calibration is suitable when the error exists simultaneously at both the minimum and maximum values of the measurement range, and the error across the entire range exhibits a certain linear relationship. However, the most accurate calibration method is two-point calibration, where the errors at the minimum and maximum values of the measurement range are different.
When calibrating, ensure the machine operates within your desired temperature range. For example, if the machine normally operates between 200 and 400 degrees Celsius, then even if the controller's calibration range is 0 to 800 degrees Celsius, you should set the minimum calibration reading to 200 degrees Celsius and the maximum calibration reading to 400 degrees Celsius. You should determine the error between these two points to ensure calibration is performed within the machine's actual operating temperature range—the machine should never exceed its range or operate at extreme temperatures.
Zero drift, or single-point calibration, refers to the range by which an instrument reading deviates from zero when the temperature changes. Zero drift should be set at the midpoint of the operating temperature range (unless the relationship across the entire range is known and therefore unnecessary, in which case it is not necessary).
Certificate
Some process engineering projects require calibration certificates to ensure calibration quality. In such cases, you may need to have a certified engineer perform an independent calibration. After calibration, the certification service provider will issue a certificate proving that your system has been calibrated and meets application requirements. In the UK, UKAS (UK Certification Services) can provide this service.
Multiple advantages
Proper calibration not only ensures that the system meets regulatory requirements, but also enables other advantages, such as reducing waste and optimizing the entire control system to achieve higher output.
About WEST
As a global expert in process and temperature control, WEST Control Solution products comprise four main brands: WEST, PMA, Partlow, and Cal. For over 90 years, WEST has provided high-performance, high-quality products to industries such as plastics, heat treatment, packaging, food and beverage, and life sciences.
WEST is committed to developing close partnerships with its customers. The company regularly engages in discussions and research with clients, fully considering their requirements in new product development to ensure their needs are met. WEST provides reliable, easy-to-use products with dedicated support staff offering unparalleled service. While offering standard products, we are also committed to continuous innovation, providing customized products to our customers, earning the support and trust of customers worldwide.
