[sdiy] current mode signals (Is everything digital?)

[Tim Daugard]

From: "The Old Crow" <oldcrow at oldcrows.net>

>   My only other comment on this topic is how I perceive digital vs.
> analog:
>
>   discrete time domain = digital
>
>   continuous time domain = analog

So now we have more complexity:

Digital time - Digital levels
Analog Time - Digitla levels
Digital time - Analog levels (think sequencer)
Analog time - analog levels (one of our past drummers)

>   As computers to perform computations using continuously-variable
> parameters were made, the term "analog computer" came along to
describe
> the widget.  When the digital computer came about, algorithms had to
be
> fashioned to characterize the previously continous varibles as
discrete
> quantities.  Now we call them programs.

This message and the on going discussion help me realize another way to
explain my current mode versus voltage control of the systems.

In a closed loop system:

Voltage is discrete (digital?) the voltage can only be measured at nodes
where to components meet. The voltages between nodes varies depending on
which node is measured (also ignoring the effect of the measuring
device.)

Current is continuous (analog?) the current in a closed loop is the same
no matter where you measure it.

By using currents to control systems, the current can be varied at one
point and measured any distance away. Signals external (common mode
signals?) to the current loop have no effect on the loop. This
eliminates interference from external signals (mostly RF). until the
signal is large enough to destroy a component in the loop (EMP?)

Tim Daugard
AG4GZ 30.4078N 86.6227W Alt: 3.7 M
http://home.sprintmail.com/~daugard/synth.htm