NLS Test Gear

From: John Lawson <>
Date: Sun Jan 7 21:02:04 2001

  Non Linear Systems has a special place in my checkered past. When I was
13, an old engineer/ham friend of mine gave me an ancient (even then it
was old!) NLS 3-digit DC DVM. I was absolutely in heaven. He said " Here
ya go, kid, her's a box o' rattlesnakes fer ya!"

  For those who care.. this DVM used an auto-nulling resistance bridge
implemented mainly with 10-pole 40-throw stepping switches. The wiper
arms had a ratchet wheel run by a pawl connected to a hefty electromagnet.
The device had one stepper for each decade (and hence, digit) with
precision resistors soldered to the the switch banks.

  Applying DC voltage to the imput unbalanced the bridge, and the switches
began operating until the bridge nulled out. One set of contacts on each
decade switch was connected to a bank of tiny 356-style flange-base lamps,
which were mounted in staggered rows in an aluminum holder. the holder was
slotted to carry 11 thin clear plexiglass or acrylic panels, about 1" by
1.5", upon which the digits were engraved. (one for a period) When the
required lamp was lit, it shone down thru a hole in the carrier for that
particular panel, illuminating it edge-on and making it stand out from the
other realtively dark panels in the stack. The last digit was a zero and
it was damned hard to see in a bright room.

  It had two rack-mount chassis, the switching part and the thinner
display unit, connected by the obligatory multi-core cable and massive
winchester connector. The switch box was entirely lined with thick felt
inside, to try and reduce the racket. I, of course, ran the thing open
most of the time.

  Any change in the input levels caused the entire system to start at
'000' and then work up to a null... the last bits of a reading would slow
and then it would stop with the result in the display window, and it did
sound like a mechanical snake.. rr-rrr-rrrrrr---r-r-tictic-tic...tic. It
was my first piece of 'real' test gear and I'm kinda sorry now that it's
gone. snif. snif. O well.

  No thanks, I don't want to buy another. I live too far away for the
shipping to make sense.. ;}


Received on Sun Jan 07 2001 - 21:02:04 GMT

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