You may remember me from before well I've done the practical now and I've
some results. I decided to use a capacitor resistor network and connect it
up to a computer with WINSCOPE (please download, it's really tiny size and
doesn't affect your computer: [Only registered users see links. ]).
I have a few queries. It shows a graph of voltage vs time. The x-axis
represents time, and I know that. What I'm trying to do is this: I have some
screen grabs of voltage discharge/charge curves, and I'm trying to find the
voltage after 5 time constants (I know where). But I need to read off the
voltage at that point, how do I do that? Does something called "Y1 Gain"
make any sense? I've no idea how to convert that nonsense into voltage.
Should I just use percentages or something? Thanks.
On Wed, 21 Dec 2005 12:26:56 +0000 (UTC), "Panther" <[Only registered users see links. ]>
Hmm, I'm not sure exactly what you are doing, but I'd
just like to point out that since this system uses a sound
card for input, it is AC coupled. That means that any
time constants you are trying to measure will have to
be much shorter than the time constant of the input
itself. The input is usually a few Hertz high-pass, but
could be up to 20 Hz or more on older/cheaper cards.
So this system probably won't be of much use in
trying to meaure time constants longer than
As far as getting absolute voltage readings, there
is absolutely no way to do this via software. The Windoze
driver doesn't consider this sort of thing in the least,
and there is no place in it for calibration values to be
returned to the program. You will thus have to do the
First, be sure you have the Windows Mixer sliders in
a known configuration. Given the crudeness of the
Windows Mixer, that pretty much means maximum
volume. Then apply an input signal of known
amplitude and read it on the trace. Use that as
the basis for your calibration. Of course, you must
keep the same mixer settings on all future uses.
My Daqarta for Windows software will adress all
of these issues, but it won't be released for a couple
of months yet. I'll post a note here when it's ready.
D A Q A R T A
Data AcQuisition And Real-Time Analysis [Only registered users see links. ]
Home of DaqGen, the FREEWARE signal generator
"operator jay" <[Only registered users see links. ]> wrote in message
news:Yamqf.7$[Only registered users see links. ]...
and [Only registered users see links. ]).
The help file you downloaded with the software says the maximum input is
about 2VAC. You could assume that your volume control sliders were set all
the way up, and then assume that the maximum levels are +-2.5V or +-3V (or
something in there) and then factor in your gain (probably Y1), and hope
that that gives you a correct scale. Not as bad an idea as it sounds. Make
your assumptions and write them in your lab report, right up front. Give
your answers in volts and in p.u. of the maximum voltage you saw.