X381: Difference between revisions
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The X381 is an experimental 560-series timebase plug-in. | The X381 is an experimental 560-series timebase plug-in. | ||
It appears to have used a [[3B1]] plug-in as a starting point. | It appears to have used a [[3B1]] plug-in as a starting point. | ||
No documentation is available for the X381 | |||
so everything in this page is just a guess | |||
based on examining the one existing plug-in. | |||
==Features== | |||
* Digital front-panel display of sweep rate in TIME/SEC or Hz. | |||
* Continuous vernier adjustment of sweep rate from the slowest rate to the fastest rate with no discontinuities. | |||
==Front Panel== | ==Front Panel== | ||
The front panel has a Nixie display | The front panel has: | ||
which is driven by a [[Fairchild 9960]] decoder/driver IC. | * a Nixie display which is driven by a [[Fairchild 9960]] decoder/driver IC. | ||
* a two-position slide switch with positions marked "SEC" and "Hz". | |||
* a TIME/DIV knob concentric with a vernier sweep speed knob. | |||
==Principle of Operation (a guess)== | |||
The rotational position of the vernier sweep speed knob is linked by shafts and gears | |||
to the rotational position of the main encoder shaft. Attached to directly to the main encoder shaft are: | |||
* a rotary optical encoder, and | |||
* a free-rotating (no angular stop) precision potentiometer | |||
Each angular position of the main encoder shaft produces a distinct pattern | |||
of illuminated or not-illuminated in the 26 optical fibers (or flexible light pipes) | |||
that exit the rotary optical encoder. These are optical signals are converted to electrical signals | |||
and the electrical signals are fed to the nixie controller ICs. | |||
Thus, as the vernier sweep speed knob is rotated, the digital display on the front panel follows it. | |||
Meanwhile, a precision potentiometer is attached to the main encoder shaft. | |||
This potentiometer functions in essentially the same way as the vernier sweep speed | |||
on a conventional timebase plug-in such as a [[3B1]]. | |||
When the rotary optical encoder is at the end of a revolution, | |||
an optical signal (one track on the encoder disk) calls for a step of the | |||
the 1-2-5 rotary sweep speed switch that is concentric with the vernier sweep speed knob. | |||
A motor and gears rotate the rotary switch. | |||
The position of the main encoder shaft (and corresponding pattern of fiber illumination) | |||
is insufficient to disambiguate which direction to rotate the 1-2-5 sweep speed switch. | |||
One possible solution would be to use memory, i.e., to continue in the same direction as recent | |||
motion of the vernier knob. | |||
The approach taken in the X381 is to use a torque sensor in the vernier knob. | |||
A pair of microswitches is attached to the vernier knob. One closes on clockwise torque; | |||
the other microswitch closes on counterclockwise torque. | |||
The direction of the torque of the vernier knob determines the direction of the step of the 1-2-5 | |||
sweep speed switch. | |||
==Optical | ==Rotary Optical Encoder== | ||
Within the X381, | Within the X381, | ||
there is an octagonal aluminum enclosure containing a backlit disk of film | there is an octagonal aluminum enclosure containing a backlit disk of film | ||