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Dew diligence: Michell instruments is a highly successful UK niche business which has built its reputation on searching out moisture wherever it lurks and measuring it.

The Cambridge phenomenon is the marketing name given to the cluster of high technology companies, many of them concerned with electronics or software, that has grown up in and around the university city.

It's cited as the UK's nearest equivalent to Silicon Valley in California, and sometimes referred to as "Silicon Fen": the gist is that the companies derive benefit from each other and from the worldwide academic reputation of Cambridge. But it's usually seen as a thought-leadership research-based centre rather than as a manufacturing hub and one of the biggest names in it, the chip design group ARM, makes a virtue out of this.

Another Cambridge company, Michell Instruments, however, is both research-based and very determinedly a manufacturer. "Were one of the few left" says director of marketing Peter Kubietz, not entirely seriously. "The philosophy of the company is to own the sensor technology because that is the heart of any instrument and if you control the technology you control everything.

"So we manufacture the sensors and the electronics and where we subcontract some of the electronics we develop it, put it together, calibrate it, develop the firmware and the application software. It's the strategy of the company to own the technology and not to buy in from other companies and rebrand things: we only do some of that to have a more complete product portfolio. But on the core we own it."

Michel! is very much a Cambridge phenomenon company spun out of the university, though its now based several miles north of the city on the outskirts of Ely: it outgrew its premises in central Cambridge a few years ago, and has already had to expand its plant again since moving.

The Michell core of proprietary technology is a broad range of instrument types that measure moisture and humidity. While these go down to the mass-market systems that are found in wall-mounted air conditioning monitors and that measure relative humidity to between 3 and 5%, the group's speciality has been in high-value high-end instruments that demand much greater accuracy and often have to be customised to meet a specific application.

The group spends heavily on research and development: that's about new products and new ways of measuring humidity, but its also about custom applications to meet the particular needs of individual customers who can be some of the biggest and moist demanding groups in the world.

Customers are in a lot of process industries, and there's growth too, Kubietz says, in the increasing use of environmental test chambers across many industries and also in businesses such as lithium battery manufacture. The long-standing areas of demand are in petrochemicals and power plants, where operators use dewpoint measurement to save energy and also to protect turbines from damage; pipeline and pure gas supply operators too want to know the dryness of the gas they are transmitting.

"Also a large part of our business is in compressed air systems which are everywhere in industry: to condition the compressed air you have to dry it and almost every drier of a certain size has some humidity control, and in many cases it would be our sensor that does it," Kubietz says.

The technology that has made Michell's name worldwide is the chilled mirror sensor, which essentially measures dewpoint rather than moisture content. In many applications, Kubietz explains, the moisture in a gas stream is only a problem when it condenses out, on the walls of a pipeline, for example, or in a nook or cranny in an environmental chamber. There it can give rise to corrosion or to bacterial growth, affecting flows, or the integrity of the system, the cleanliness of the cleanroom or the purity of the gas being supplied.

There are quite a lot of aspects to this, and at the high end there are no really standard applications. "In some applications, its about corrosion, so if the gas contains moisture particles that are in a gaseous state it's not as bad as when it condenses, and it condenses because the temperature goes down--so you could have day and night temperature variations in a pipe system that could cause you problems," Kubietz says.

"But in other applications you might want a certain moisture and condensation level because you want your cookies not too dry and not too moist. So moisture has to be maintained at a consistent level for the product to meet its quality demands."

Michell's technology encompasses several different types of device which it makes in Ely and in subsidiary plants. "Starting at the wet end, we have capacitive sensors which we make in our French subsidiary plant and for low moisture we have the so-called ceramic sensors we manufacture in Ely. Then we have the chilled mirrors which we also make here and recently we extended the portfolio with quartz crystal microbalance sensors that quickly and precisely measure moisture content, which is a new approach for us."

Future systems are likely to involve laser spectroscopy: Michell has a research partnership with three UK universities, led by Cambridge, that is aiming to develop a system that can be "tuned" to identify the moisture spectrum specifically.

The chilled mirror technique for which Michell is best known measures dewpoint. "In simple terms, there's a mirror that can be chilled to a given temperature and an optical system measures the condition of the mirror in terms of condensation," Kubietz says. "When the mirror starts to form condensation the system will identify that this is the dewpoint of the given gas that's being measured."

Accuracies to within +/-0.1[degrees]C are achieved, so one of the major roles for this kind of sensor is to act as a reference instrument from which to calibrate other instruments. "These are mostly bought by people who want to test their own systems, but they can be sold to anyone who needs to have more precise measurement," Kubietz says.

This is a niche in the test and measurement sector, but it's a growing one. Tighter controls over the moisture inside systems is not just a growing regulatory requirement, it's also environmental sense. In a compressed air system for example, Kubietz says that a drier controlled by temperature measurement alone or by some electronic algorithm is "basically blind" and will switch in and out whether it needs to or not; control by moisture gives up to 30% better energy efficiency, he says, by switching only when really needed.

Growth has also come from new demands in industries such as aerospace and automotive, where processes for handling new materials such as lightweight or thin-section steels are far more closely controlled in terms of the humidity than the standard processes. And there's been big geographical expansion too: Michell has taken on its own direct sales in some growth markets rather than use agents.

It's a niche too, that isn't likely to go away. "It's one of those things that you really can't simulate," Kubietz says. "You have to know what's in your gas, and you have to measure it."

RELATED ARTICLE: The importance of calibration

An important part of Michell Instruments' business is the calibration of its own and its customers' instruments, and the company has long-standing links with the baseline measurement standards that are the responsibility of the National Physical Laboratory.

There are two main areas where calibration as a service is wanted, says product manager Auberon Tatum. "It's to provide reference instruments for people who want to do their own calibration and for instruments where the industrial applications can only be filled by chilled mirror," he says. "So there is quite a lot of monitoring in environmental chambers in industries such as food, pharmaceuticals, aerospace and other product testing where this is needed. There's quite a big demand for better certainty which isn't always met by the traditional psychrometry methods. There are a lot of regulations nowadays that are encouraging people to move to higher accuracy."

Current regimes for engine test cells, for example, are fairly relaxed in terms of relative humidity measurement, at 2-3[degrees]C, "but for future norms you're going to have to be very precise, because the uncertainty of the whole measurement takes into account the uncertainty of the moisture sensor taking the humidity in the chamber, so if you try to squeeze every possible per cent out of that the less the overall error will be." The latest specs for engine testing call for an accuracy of +/-0.5[degrees]C dewpoint: "We've tested some going to Japan and there's no choice but to use chilled mirror for this kind of accuracy".

The calibration work, says director of marketing Peter Kubietz, is time-intensive: "It takes 10 days to do it." The calibration starts with the purging of the system to eliminate all traces of moisture: "This isn't easy," Kubleiz says. "Moisture molecules use any opportunity in pipework to cling to the walls, so it takes days to dry the system down completely. We then start wetting up to 12 measurement levels starting at -100[degrees] and going up to +20[degrees] in 10[degrees] steps."

A large area of the site at Ely is turned over to the calibration which Michell offers as a service to customers, for its own sensors, and even for competitors. "The calibration is traceable to NPL standards via our system, so customers can take a reference instrument and then do their own calibrations." But the company has also set up an exchange system for customers to send back their instruments with a freshly calibrated one sent back, and the scale of the calibration operation at Ely offers opportunities in terms of system automation and local expertise that aren't easy to replicate.
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Title Annotation:Test & Measurement
Publication:Environmental Engineering
Geographic Code:4EUUK
Date:Dec 1, 2013
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