My return to Classic Cmp - San Diego, software archive, etc.

[Tony Duell]

> In the early days of my youth (pre computer), I worked as an 
> instrumentation technician.  Many chart recorders, such as L&N 
> Speedomax,  used a "slidewire" that resembled a single-turn wirewound 
> potentiometer.  But the Honeywell Brown Electronik recorders used a 
> multi-turn helical pot about the size of a coffee mug.   I never 
> understood why they were referred to as "slidewires" and not 
> "helipots".  It was not uncommon for the line operators to steal the 
> silver bead used as a contact in those.

I have the mechanism from an old chart recorder, I beleve a Honeywell, but
modified by Pye Unicam, which has 2 feedback pots. One is the normal
linear slidewire mounted across the chassis (the slider being on the pen
carriage. The other is an accurate logarithmic pot driven by a pulley on 
the drive cable that links the motor to the pen carriage. I also have a 
little box of electronics containing a cathode followe buffer and a relay 
to switch between the 2 slidewires. The insturment, of course, could 
either have a linear or logirithmic pen movement.


-tony