16 Dec
2008
16 Dec
'08
11:04 a.m.
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