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Producing infrared thermometers that work

Good engineering makes the difference

It's so simple: aim the laser pointer, pull the trigger, read the temperature. But the easy operation of Fluke infrared thermometers doesn't just happen.

It takes months of product planning, design and development to achieve the combination of accuracy, price, dependability and ease of use that characterizes Fluke tools.

From idea to finished design, even for a modest upgrade of an existing product, development can take more than a year, said Fluke product planner Samir Jain. Creating a whole new product takes even longer.

Through it all, the design team makes dozens of decisions and tradeoffs needed to build a rugged, reliable tool with the highest performance possible, at a price buyers consider a good deal. Fluke's rigorous in-house development process contrasts sharply with many competitors, who merely repackage tools designed and built by others.

Hearing the Voice of the Customer
It all starts with an idea: a need customers have for a new tool. For instance, a new infrared thermometer designed to achieve better range, include advanced features and be even more durable than existing models. The initial product concept gets a big injection of reality through what Fluke calls the VOC: Voice of the Customer. "I do a lot of talking to Fluke customers and talk to customers of other manufacturers as well," Jain said. "We'll talk to people who have used the tools — what do they like and dislike about the ones they currently have. We spend a lot of time determining what the customers want, and also what they don't want. One of the things we focus on is making the product easy to use. A lot of our competitors will put more features in these products, but you talk to the customers and they seldom use them, oftentimes because they can't figure out how."

Using this VOC input, product planners begin to quantify the many possible features and performance characteristics, to determine how valuable they are to customers, and how much they would add to the final price of the tool. "We put together a rough set of customer requirements," Jain said. "We say we need to price it around here, and we need to have these capabilities and features."

Now the planners start working with the engineering team. Which features can be included without exceeding the price target, slowing the product rollout schedule or introducing complexity that makes the product harder to manufacture and can impact quality? "We do a schedule of risks, including manufacturing risk," Jain said. "Is this thing manufacturable? What are the challenges? And we look at development risk. Are there certain things we've never done, or we know would take too long?"

Shaping the Things to Come
Next to get involved are the industrial designers, who develop concepts for the shape of the new tool. "Ergonomics, secure hand holding and easy triggering are the big elements, along with ruggedness," said Medwin Schreher, engineering manager for Fluke portable infrared thermometers. "We're really focused on making it easy for the user to aim, and that has a lot to do with shape."

Infrared thermometers typically take three forms. Some are flat, shaped like a TV remote control. A few are held up to the eye like a movie camera. But most are shaped like a pistol. "The dominant form factor for us is the gun-style shape," Schreher said. "You can point and aim it while it is comfortable in your hand." There's also a safety factor at work, since the movie camera design can obscure the user's vision when it's held up to the eye.

Fluke FoodPro thermometers are shaped with a right angle between handle and sensor, to make it easier to test horizontal surfaces like food containers. The Fluke 561 uses a more typical pistol shape for both horizontal and vertical readings. Displays also get close scrutiny. Overall size, viewing angle, character size and contrast all are serious considerations for performance and user comfort.

The give-and-take continues as designers and engineers review the design proposals in brainstorming sessions, suggest changes and add ideas. "We usually get down to a choice of two or three designs, then make three-dimensional models," Schreher said. "You have to do that these days." Designers send computerized drawings through 3-D copy machines that build full size models in plastic or starch. If a picture is worth a thousand words, these mockups are worth a thousand more when firming up what a tool feels like in the hand.

A Gathering of Engineers
"At this point we're starting to talk with all the engineering teams," Schreher said. "Are we going to be able to fit the technology inside this shape to do the functions we want it to do? What kind of risks do we have for sealing and drop testing and optical performance and so on?"

The project team draws engineers from a variety of disciplines: mechanical, electrical, software, firmware and systems engineers all collaborate to fine tune the emerging design. They use guidelines drawn from past experience to control trigger pressure, feel and countless other factors, but in the end, Schreher said, there's no substitute for building a prototype and having people test it.

Meanwhile the team is planning the inner architecture of the tool, working to minimize the number of parts, reduce costs and make it easy to manufacture without error. They minimize wiring and replace screws with snap-fit connections. They assemble electronic components on a "bread board" and test their performance. Thousands of design choices must produce a tool that will live up to Fluke's reputation for performance, ruggedness and reliability. As Schreher puts it, "every component is a product or system in itself." And every component goes through Fluke's torture-testing lab, where it gets roasted, frozen, soaked in humidity and worked until it fails. Then it's strengthened, and tested again.

As the go-to-market date approaches, tooling is completed and pilot production begins to fine tune the manufacturing process for yield and quality. Now the design is set, but testing is not complete until prototype products go through a round of lab tests, as well as final Beta testing in the hands of customers. And yes, said product planner Jain, sometimes these customer Beta tests do result in changes.

With Beta testing complete, the new infrared thermometers cleared for shipment. Technicians across the world will have a new Fluke tool in their hands. And though few will know about the process that created that, they will care deeply about the results — the precision, ruggedness and durability that make their jobs and their results the best they can be.

Heat Up Your Infrared Knowledge
An infrared thermometer is one of the most versatile tools you can own. But to get the most from it you need to know how it works – what it will do, and what it won't.

IR thermometers measure invisible infrared light – part of the light spectrum you can't see but can feel, as heat. Infrared radiation was discovered in 1800 by the famed astronomer Sir William Herschel, who also found the planet Uranus and first described the Milky Way.

Infrared rays are emitted from every surface warmer than absolute zero, but not all surfaces can be measured accurately by many infrared thermometers. Why? One reason is that surfaces vary in their 'emissivity' – the amount of infrared radiated at a particular temperature. Flat finished surfaces have higher emissivity than glossy surfaces, such as chrome.

Some high-end thermometers are user-adjustable for emissivity, but most are calibrated at the factory to read accurately on the most common materials — flat-finished surfaces such as fabric, paint, wood and dull metal. They will not measure polished surfaces accurately, or measure through glass, because glass can block infrared radiation. To measure such surfaces, stick a piece of flat finished adhesive tape to the shiny surface (being careful that the tape will not burn) and point your thermometer at the tape.

Another point to remember: infrared thermometers measure surface temperature only. Point the tool at your lunch cooler, for instance, and you'll know how hot the surface is, not what's inside. Your sandwich inside could be 45 degrees, but if the cooler's surface is 70, that's what the thermometer will read.

To get the best measurement results, correct user technique is important.