Re: 60Hz noise making it's way into my test


John Popelish wrote:
SklettTheNewb wrote:
jpopelish@xxxxxxxx wrote:

SklettTheNewb wrote:

Hi John,

I would like to reply inline, but I'm using the google website for this
and it won't show me the orginal message. Apologies for my bad
formatting.

THis is also posted from Google Grpups. You have to select "Show
options" at the top, instead "Reply" at the bottom, then "Reply" at the
top, to have the previous post quoted. It is not well explained on the
site.

:0)


To answer your questions:

"Is that 0 to -25 or 0 to +25 volts?"
0 to +25 volts

Okay. What voltage swing does the counter input need?


From what I see on the spec ***:
"input low voltage: 0.8v max"
"input high voltage: 2.0v min"

I think this means that any voltage below .8 volts (but above zero)
will be interpreted as a logic low, and any voltage above 2 volts (and
probably below 5) will be interpreted as a logic high. Any voltage
between .8 and 2 is not guaranteed to be interpreted as one state or
the other.


I'm figuring that this counter wants a DC signal, so I would need to
rectify the AC square wave (from what I have read and been told).

I think you might be able to just divide the 0 to +25 volt wave to a
something like a 0 to +5 volt amplitude with to resistors and
connected that smaller signal directly to the counter. A pair that
might work would be 10k to the 25 volt signal, and 2.4k to ground.
The junction of those two resistors should provide a 0 to +4.8 volt
signal.


I really want to do that :0)
We had hired a consultant to make a basic application to show how to
interface with the acquisition hardware. I could have figured it out,
but decided that it would be more efficient to pay someone to "jump
start" things. Anyway, long story short, for a reason that I can't
remember at this time, the consultant said he couldn't use the counter.
He told us we would need to calculate it based on the analog voltage
values read in.

We are squeezed for time so accepted this. So as of this writing, I'm
just trying to get the system that he delivered working and in use.
Then, when I have a little time, I want to do exactly what you said,
divide things way down and try and use the counter, which I would hope
is much more accurate that counting analog edges like I am now.

I will look into the ground issue you had mentioned. Thanks for
reassuring my suspicions that the counter is a good way to go or
atleast worth another look.

-Steve

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