Those are pretty good solutions, and I'm becoming more and more optimistic
here. And, to answer the question, time is a bit more expendable than money.
Make that alot more. We have several months to build this thing and are down
to our last dollars for now, and about the only obstacle left is force
measurement. Actual construction on the tunnel itself is going so smoothly
we're certain we've done something wrong. The diffuser is finished, the base
structure is just about finished, the fan is mounted, and the test section is
well under way. A trial run with the fan and diffuser went well. Frightening.

-Tony

<< The quick and dirty solution is to use a couple of cheap ($50) digital
 postal scales (or equivalent. I saw a digital fish scale for $28C some
 years back).
 You can easily pull out the load cell and remote it with some heavy guage 4
 conductor shielded wire. You can read the LCD data by XORing the segment bits
 with the BP signal (effectively removing the driving square wave). Use a PIC
 to dedode the segments. IIRC you only need 5 segments to uniquely
 identify what digit is being displayed.

 There are also cheap ($15C) digital tire pressure guages that could be hacked
 to stay on all the time. You may want to crank up the gain to get finer
 resolution.

 A varient on the current balancing of meter movements to measure microgram
 forces is to use a small loudspeaker with linear optointerrupter for
feedback.
 An 8" woofer can generate 10's of grams of force continuously if you blow air
 through the coil gap.

 What's your time worth compared to buying a commercial nearly turnkey
solution?

 Robert
  >>

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