MEASUREMENT + INSTRUMENTATION
equipped with an integrated explosion protection function. These instruments no longer have to do with modified laboratory equipment but are specially designed devices characterised by streamlined commissioning. Because they still require climatisation, however, they are far removed from a compact field instrument solution. Another important milestone on the path to the process is the integration of an industrial embedded computer with direct connectivity to the control system. This approach offers more process compatibility through an extended operating temperature range. Users can install the solution close to the process. However, connectivity to the process medium still requires optical measurement probes and fibre-optic lines. These types of already highly integrated systems stand out due to much faster commissioning and simple operation. New technologies make it possible Making the decisive step in the direction of compact field instruments calls for newer or different technologies for the spectrometer components. The elimination of fibre optics and the integration of measurement probes in an inline spectrometer promises a more streamlined solution. The use of cost-effective standard components from conventional field instruments such as field enclosures, embedded computers, displays or compact transmitters offers further savings potential. By exploiting every possibility, manufacturers can deploy process spectrometers as compact field instruments that are much simpler to use and, importantly, can be operated at a lower cost. An example is the compact Rxn5 Raman process analyser for measuring gas. This mechanically robust instrument fulfils all explosion protection requirements and features solid state cooling and an embedded computer. The autonomous Rxn5 is not dependent on an external infrastructure. Chemo-metric models are already pre-built for many applications or they can be created for a specific application if needed. With this compact, integrated solution, users can easily and cost-effectively carry out transfer custody measurements of liquid natural gas (LNG) flows, for example. While this analyser is on its way to becoming a field instrument, the spectrometer components still correspond largely to those of a conventional laboratory spectrometer with a fibre-optic connection to the process, which is the reason for its large and heavy design. Towards the finish line Endress+Hauser has developed process spectrometers that take full advantage of the opportunities innovative technologies offer. These instruments simply constitute an enclosure, a process connection and an integrated measurement probe. External fibre-optic lines are superfluous. A microprocessor autonomously controls the sensors, analyses the data and outputs the process parameters, including the status. Extensive processing power puts intelligent data analysis within reach. The process spectrometer is connected to a standard transmitter
greater numbers. Lab informa- tion and management systems (LIMS) provide reliable pro- cessing and documentation. Generally speaking, such lab instruments are set up sep- arately, optimised for the lab and not integrated into the pro- cess control system. The major downside is that the samples from the process can change while being drawn, during transport and through the cor- responding delay. The time lag of several hours or even days means the lab analysis is often no longer current. Operators have no chance to carry out timely corrective measures or regulations while the process is running. Compact field instruments, on the other hand, are de- signed especially for direct use in the process. In respect of ingress and explosion pro- tection, as well as hygiene,
The Rxn5 Raman process analyser is a turnkey solution for quantitative measurement of chemical composition.
their performance is exemplary. They are integrated into control systems and can handle complex calculations. The requested measurement value is available in real-time and can be regenerated with a repetition rate required for pro- cess dynamics and used for control purposes. As a further factor, the field instrument also supplies the status of the measurement value and the system. That means the measurement unit allows intervention in the process control system. As all the components are integrated into the sensor or transmitter, installation and maintenance requirements are reduced, and can be driven down further through an automatic cleaning or calibration unit. Self-diagnostics simplify operation and, in the best case, provide predictive maintenance information. The integration of internet-capable devices in cyber-physical systems creates further optimisation potential. Stepping into the future Taking the first step in the direction of field instruments often involves a modified laboratory instrument. A somewhat more compact version of a laboratory spectrometer is connected to the process via optical measurement probes and longer fibre-optic lines. A separate industrial PC assumes respon- sibility for the data analysis and system integration. The re- quired ‘climatisation’, including explosion protection, can be implemented either in a climate-controlled cabinet or a sep- arate analysis enclosure. Commissioning and overall invest- ment costs can nevertheless quickly add up to six figures. One step closer to the process involves spectrometers in a significantly more robust mechanical version, which are
18 Electricity + Control MARCH 2022
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