Testing times05 April 2012

The power of sensing systems today is to be found less in the range of techniques, technologies and hardware designs, and more in their on-board software. Brian Tinham reports

If there is a story to tell generally across sensor technology, it is not so much that new or better devices are enabling more precise and repeatable measurement of greater ranges of parameters. Nor is it that miniaturisation and improved manufacturing techniques are together packing ever more power into smaller envelopes. Both of these statements are undoubtedly the case, but even more noteworthy is sensors' increasing scale of intelligence, with software enabling enhanced auto-diagnostics and calibration, as well as wireless and remote communications, and intuitive HMIs for set-up and display.

The fact is that sensor systems – whether monitoring physical, electrical and chemical parameters, for monitoring or test purposes – are increasingly now 'plug and play' items. On the one hand, that means plant technicians, not only skilled instrument engineers, can handle everything from installation to commissioning, operation and maintenance. On the other, hitherto uneconomical monitoring has in some cases become entirely feasible. And the result: plant, and for matter maintenance, operations can run more efficiently; uptime can be improved; and so can health and safety.

Auto-sense validation
Take Emerson Process Management's Rosemount 848T temperature transmitter, which is equipped for Foundation fieldbus digital plant communications. The device now sports that company's so-called Measurement Validation diagnostics, which automatically detects measurement and process abnormalities, so allowing users to take preventive action and avoid shutdowns, process inefficiencies and potentially even safety issues.

The point, clearly, is that temperature sensors, such as thermocouples and RTDs (resistance-temperature detector), degrade over time – particularly under harsh process conditions. So, using the new transmitter's inbuilt intelligence to continuously analyse variations in the signal, the diagnostics catch sensor problems long before they become catastrophic. What's neat is they also automatically detect changes due to electronic interference, corroded terminations, loose connections – and, really clever, process upsets. Quite simply, the software calculates the process rate of change, so helping users detect reactions that are starting to run away, before alarm thresholds are transgressed.

But this kind of advance is not restricted to temperature sensing. Emerson has also introduced a configuration and diagnostics tool for its Coriolis flow and density sensing meters. Micro Motion ProLink III is its nattily named configuration, data logging and service tool, which can be driven by anyone familiar with Microsoft Windows. Essentially, you see process variables and alerts via a single diagnostics display, and the system automatically identifies fault conditions and prioritises them according to severity. What's more, the guided connection wizard, simulated device feature and the configuration tool help to reduce commissioning time and start-up costs by limiting the opportunity for mistakes.

Meanwhile, Endress+Hauser's newly launched Promag 53 flowmeter has an integrated web server and EtherNet/IP for remote and local digital plant connectivity. Not only that, but configuration, monitoring and diagnostics are all delivered by Rockwell Automation's PlantPAx process management system, under the two companies' long-standing development partnership.

As with all electromagnetic flowmeters, this one is designed for electrically conductive liquids (> 5 µS/cm) primarily in the food and beverage, water and wastewater, and similar process industries – and it sports FM/CSA Class I, Division two approval, while also fulfilling EMC requirements to IEC/EN 61326 and NAMUR NE21. But just look at the functionality: using EtherNet/IP, up to 10 variables can be configured, including volume flow, calculated mass flow and totalised flow, for remote access.

"Promag 53 is engineered to integrate seamlessly with the PlantPAx system via a downloadable Level 3 add-on profile," explains Jerry Stevens, flow product manager at Endress+Hauser. "The integration is as simple as using a USB stick and, due to its plug and play nature, the integration can be copied and pasted, so that the initial work is done only once."

Talking of USB sticks, many suppliers are now offering these as a preferred storage medium for product and associated reference data, in place of printed documentation or web-accessed PDFs. Fluke, for example, is offering a free USB thermography stick, which it describes as "an exclusive gateway to access everything the professional electrician and industrial maintenance technician needs to know about thermal imaging". What that means is videos, a digital copy of Fluke's 72-page booklet 'Principles of Thermography', an ROI (return on investment) calculator, links to online training etc.

As for the future: expect to see more wireless sensors and energy harvesting devices to power them. The former are already widely adopted in the automotive sector, especially where active RFID sensors are concerned. But mainstream process companies, such as ABB, Emerson, Honeywell and Siemens, are also supporting WirelessHART (the most widely adopted digital plant technology) on a range of process transmitters.

Industrial environments are also rich in vibration, so energy harvesters harnessing that source, for powering sensor batteries, are already well into the trials phase. Other sources will follow suit, and, as prices fall, powerful wireless sensing – including machine vision – will become even more affordable.

Brian Tinham

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