This is a re-visit of the device and this web page, 25 years later. Digital photographs are trivial now where they used to be expensive. I had a 27K-bit modem back then to upload with and today I have gigabit fiber, and storage, who cares.
This is one of my favorite boxes. It is in good working order, though the display-selection was screwed up for the last few or ten years; it forgot how to stop on the correct images. The cause turned out to be corrosion on the connector pins for the ancient DDU displays; a wire brush and DeOx-It solved the problem. (And revealed a flaw present since built; a missed solder joint finally went intermittent.)
There are now many photos of the innards, taken in June 2024 when I had it apart for repair. I was really into brass then, lol. And laced wiring. Most of my boxes look nice inside, to me it's as important to the work as the outside, or the function.
Model 71 Measuring Device really does measure; the outcome may be dubious but it really is passing current through the sample and calculating a result. It's not my fault if you cannot correctly interpret it. My job is done though I'm still waiting to get paid...
Here are many detailed images of the device and its innards and some descriptions of the components and methods.
Here's some video of the machine in operation. The first two are of the DDU units (I should pick one video).
This is a simple long take in dire need of trimming down to 10 to 20 seconds, but I've just switched (back) to linux for my desktop and don't have a simple video editor yet.
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The instruction card attached to this instrument says it best:
"The Model 71 is a portable standard for calibrating once-living and non-living organic substances. It accepts a wide range of inputs and may be used with a minimum of surveillance... Only a small quantity [of the organism] is needed; a small portion may be removed with little harm to the subject."
While the Model 71 performs its intended functions with hopeful grace, it leaks out hints of its cultural inheritances and intents (intentional and otherwise). Some things are reasonably visible, but others might remain obscure to those outside the priesthood; this instrument of deduction is tightly focused and utterly unaware of its own context, unsure of its own authority, unable to relax and just get the job done.
A sample is prepared, according to excruciating instructions on a card in the front cover, and placed into the complicated and delicate probe mounted in a little door in the front of the machine. The operator carefully adjusts a calibration control as instructed, and the machine is set to run; the Model 71 then performs a number of calculations based upon actual electrical measurement of the sample.
(If none of this manual preparation is actually done and the machine is left idle, it will occasionally find things to do of it's own accord.)
Physically, the Model 71 is constructed of excruciatingly correct and luscious materials and components; veneered cabinetry, deep-etched copper plate, bakelite knobs; delicate glass, rubber, and nickel-plate probe assembly, an ancient and beautiful electro - mechanical graphical displays (for presenting the symbolic results of the calculations) and an optical "single plane" display for operational status.
The cabinet once housed a Beckman portable laboratory pH meter; the sample-measuring probe assembly mounted inside the chamber on the front of the unit are original, though modified to use nontoxic solutions. Test vials and a bottle of reagent needed for testing (including a recipe for the preparation thereof) are contained in a pouch within the removable cover. The front panel is quarter-inch-thick copper plate, deep-etched and corroded, hand-machined to accommodate the display units and controls. All other hardware is brass and new-old-stock phenolic.
Mixed media (wood, brass, electronic
components), 10.5"h x 11.25"w x 8"d, approx. 15 lb.
