Re: Alternating Current (III)

[brian whatcott <inet@INTELLISYS.NET>]

At 16:43 1/29/99 -0500, David wrote:
> ...use a CBL to look at the
> light intensity from an incandescent bulb sampling every .0001 seconds
> for 100 data points.
>
> ... the calculator shows a beautiful sinusoidal graph
> and the regression analysis shows an excellent fit with supporting
> residuals.
>
> However, I would have expected to see a graph more like |sint| which
> should not look like a sin but should have the frequency of double the
> line voltage frequency ...

>        David Abineri

It was only after carefully reading Bowman's splendid analysis
which itself pointed back to Haar's cerebrations (delivered in
such a quiet, steady manner it was easy to overlook them for
some reason...) that I realised I was completely ignoring Abineri's
 initial remark about a function called |sint|.
  And I was ashamed....

 What he had in mind was something familiar to me as |sin(x)|
but what *I* was registering was the math function representing
'double length to single length integer conversion'
   Functions like these, sint, dint, fint are to be found in some
 vendor implementations of programing languages like Fortran.
And yes, it didn't make much sense so I skated over it.

 I expect I was the only list reader that construed |sint|
as anything other than 'Absolute value of a sine function of time'.

The electrical person immediately recognizes this as a description
of a full-wave rectified wave; in this context, Abineri's question:
"Why does the signal look like a sine wave rather than a FW rectified
sine wave?" is answered explicitly when Bowman responds,
" The higher frequency components of the light intensity envelope are
greatly attenuated by the physical conditions at the hot filament."
 In these circumstances, any periodic wave reduces to a fundamental
sine form. Of course!

If there is a lesson to extract from this confession, it is
"Assume nothing: explain all abreviations and conventional symbology."

Sincerely
Brian
brian whatcott <inet@intellisys.net>
Altus OK