Calibration
MINOR INVESTMENTS IN SENSOR QUALITY PROTECT MAJOR ASSETS
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Sensor specification is an important consideration when choosing process monitoring and control equipment. However, in the following article, Juhani Lehto from Vaisala explains why the quality of a sensor can be difficult to determine from a spec sheet alone.
he cost of high-end sensors can be negligible in comparison with the processes and assets that they help to manage and protect. Process managers should therefore invest in measurement technologies that have been proven to deliver stable, accurate reliable measurements in the long-term.
SENSOR SELECTION
The suitability of a sensor for a specific application can be determined by a quick examination of its datasheet. For example, the sensor will need to operate within a known range of temperature and pressure, it will provide an acceptable output signal and it will deliver measurements within a claimed level of accuracy and precision. However, there are several important factors to consider when choosing sensors. Beyond accuracy, these include stability, reliability, and any variance in performance due to process or environmental conditions. Stability is perhaps the most important criterion because sensors must be accurate and reliable even
in demanding environments, following installation and in the long-term. The specifications of different sensor suppliers may state similar accuracies, but this does not provide insights or verification of sensor accuracy after one year, or several years. All sensors drift, but some drift more than others, and some drift more quickly, while others have good stability with minimal drifting, maintaining measurement accuracy for years. Therefore, the stability of sensors should be the most important factor to consider because it influences performance and costs over a long time and is reflected in calibration and maintenance requirements. Given the potential costs of long-term unreliability, it is important to consider the lifetime cost of sensors, and not just their purchase cost.
In addition to good stability, high-quality instruments are also easy to maintain, calibrate, adjust, and fine-tune, which lowers lifetime costs and is good news for operation and maintenance staff. Having convenient tools for verifying and maintaining the sensors and transmitters enhances reliability and provides peace of mind throughout the life of the instrumentation.
THE COST OF INACCURACY CAN BE LARGE Cooling represents a high proportion of the costs and carbon footprint of running a datacentre. Vaisala participated in a datacentre trial to simulate how much more energy would be used if there was just one-degree of temperature measurement error, causing excessive cooling. The results showed that this one-degree of error increased energy consumption by more than 8.5 per cent. Given the size of modern datacentres and assuming the same deviation can take place over a decade, this seemingly tiny error translates into many millions of euros of extra costs, particularly if server uptime is affected. Vaisala Echo measurement infrastructure brings enterprise muscle to SMEs Traditionally only large corporations have had the resources to build measurement infrastructures with advanced features such as remote monitoring, firmware updates and easy scalability. Vaisala Echo connects Vaisala measurement devices and monitoring software to create an intelligent measurement infrastructure,
March 2025 Instrumentation Monthly
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