First Law. Contacting vendors turns out to be a golden opportunity for the young engineer (any engineer?) to learn not only about the vendor's specific product line, but about the type of product in general. At first, it's likely that the product you are shopping for has more characteristics than you need to know for your application. (If you're looking at a menu, you choose your dinner on the basis of cost and what's in it -- not on the individual "Nutrition Facts.")

In one example, a contributor was looking at load cells, and one load cell manufacturer gave specs on the following: rated output, excitation, accuracy, linearity, hysteresis, repeatability, zero balance, creep, operating and storage temperature, thermal effects, maximum load, bridge resistance, deflection, materials used in construction (both of structural and electrical parts), height, weight, bore, compatible meters, rated capacity, and cost. The contributor's interests were rated capacity, geometry and cost. That other stuff is listed in the catalog for a reason, and no doubt that reason is related to some customer's needs. Knowing what others care about in their purchases may guide you in a purchase down the road, when your own requirements are more severe.

Talk to vendors on the phone. You can nearly always learn about how their thing works, and what you should be looking for in a purchase. In another example, a contributor was looking for electric winches for pulling wire rope. The first vendor explained why the winch's drum size is closely related to its rated pull and power draw. The second vendor explained why the rated pull of the winch is only about one-sixth to one-fifth the rated strength of the cable. The third vendor explained how a winch can backdrive, what the consequences are of the backdrive and how to avoid potential problems in winch selection. The contributor also learned also about grooved drums, mounting technique and noise.

Use vendor catalogs. They can contain a wealth of knowledge of product fundamentals. The Editor has not seen a large number of them, but he recommends as examples Omega Engineering catalogs because of the info they contain about fundamentals of sensing devices; and the National Instruments "Instrumentation Reference and Catalogue" for data acquisition fundamentals. Best of all, such catalogs are to be had for FREE.

Design spec sheets for your application. In the winch example, info sheets listing requirements on winches, and on wire rope, were faxed to dozens of companies in each of the two areas. This task quickly eliminated three-quarters of the possible companies from contention. Which leads to the Second Law.

Second Law. Why will you find so many companies in the area you are looking for?

• You may not be sure who to contact up front, unless you have done this before.
• The trade literature doesn't list vendors according to your specific needs. For instance, the Thomas Register lists over a hundred companies under "Winches: Electric." Although the Thomas Register has a search engine at its Web site, which will reduce the number somewhat, the reduction will not specialize your search any further. No search engine is smart enough to recognize your requirements.

At the Chinese (for example) restaurant, if you tell the person taking your order up front that you require your meal to be spicy, contain no shellfish and no MSG and no baby corn, then that helps you get a meal to your liking with no long wait and no surprise cost. In the same way, the faxed requirement sheets may keep you from having to call each company individually -- and no doubt from playing "phone tag" with some. You may even locate a company with something on the shelf that meets your needs. Which leads to the Third Law.

Third Law. If you choose something off the menu, it may cost more, it may take longer, and they may not even have it at the restaurant. The same contributor encountered this when trying to purchase conduit for the wire rope. The wire rope was aircraft cable -- which has a rated diameter with a tolerance of ten percent -- the "rated diameter" is actually a "minimum." They wanted conduit that would permit the cable to pass without slop, but would also accommodate the relatively huge tolerance in cable diameter. (This is expensive.)

Buy multiple related items from the same supplier when possible. You may (in this example) find you are better off buying both cable and conduit from the same supplier -- even if it means letting a spool of aircraft cable go to waste. If a vendor doesn't have what you want, that vendor would either not bother to respond or send a polite "decline to bid."

Let the vendor be the expert on the vendor's product. Our relationships with vendors can make us more productive, by actually eliminating the need for our project engineers themselves to be experts on the type of product the vendor sells. Follow as much as is practical the vendor's recommendation.

Fourth Law. Why should it be that a vendor (whom you have never met) would be interested in your success? Because if you succeed, and if you attribute your success (in part) to that vendor, you will do business with that vendor for a long time. A satisfied customer is worth more than Gold-Pressed Latinum.

If you pay your bills early, you can get a line of credit later. If your bills are small and your product especially promising, you may get that line of credit early. Don't hesitate to ask for it -- but be careful how you approach it. You must remember the First Law of New Technology: no-one wants to be the first to buy it. So in approaching vendors, as you would in approaching potential investors, you must concentrate on the promise (and the market niche) of the technology, rather than on its developmental aspect.

Don't hesitate to let the vendor know how you're doing. Establish a personal contact at the vendor's shop. (Most will want to give you one. That person will probably be referred to as an "account representative," or something like that.) If you have a personable relationship with that representative, then you have an advocate at the vendor's shop. Comes in handy.

Characteristics of "Good" Vendors

These are in alphabetical order. You can decide which are the most important for your needs.