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MODULAR INSTRUMENTATION DESIGN

Part 1ýDefining the Project
by Bob Perrin

Start • The Problem ý The Solution ý Mechanical Interface ý Man Machine Interface ý Electrical Interface ý API ý In Closing ý Sources and PDF

THE PROBLEM

When a small firm or entrepreneur decides to create a new instrument, several factors must be weighed. Development cost, unit cost, time to market, opportunity cost, and prolonged overhead must all be considered. In niche instrumentation markets, the cost of finished products is often high because they are highly specialized, low-volume devices.

The manufacturers of these niche products are less sensitive to per-unit cost than manufacturers of mass-marketed consumer goods, often making competition scarce. When products compete, it is often on feature set and not so much on price.

Time to market, opportunity cost, and development cost are usually the biggest factors niche companies are concerned with. A product brought to market quickly minimizes opportunity cost and maximizes the productýs impact on the market. The sooner the product is selling, the sooner the development cost (NRE) can be recouped.

Existing embedded-control products seldom have exactly the right I/O mix for an end application. Meaning, the developer must not only purchase a controller, but also buy or build additional expansion modules, making the system physically awkward. It also increases the amount of time and money that must be spent on both the electronics and mechanical packaging.

Most embedded-controller companies do not provide power supplies. At best, you might find an embedded controller company willing to sell you an overpriced wall-wart (AC/DC converter).

What about finding the right "man-machine" interface? The developer may find his embedded-controller supplier willing to provide some form of LCD or keypad. However, often this portion of the project is left to the developer to design and test.

With existing off-the-controller products, the developer must still buy or design electronics for sensor, machine, and human I/O. He must mechanically package the hodgepodge of gadgetry, and then he can focus on firmware development. All of this dramatically increases time to market, development cost, and opportunity cost.

At the end of a project, developers often discover that it would have been less expensive and mechanically more elegant to just create the systemýs electronics from scratch. The problem is to come up with a system that is flexible enough to suit the developerýs application, enabling him to get just the right I/O mix. Impossible? Perhaps.

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