Help with Winscope/Voltage things

Just do the arithmetic. Since this is crossposted to basics, I'm going to go ahead and look up the formula for you, just because I'm such an insufferable sweetheart. :-) You do remember that T = RC, right? Well, the voltage at 5T ...

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Have Fun! Rich

Hello everyone

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:

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.

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 calibration manually.

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.

Best regards,

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

On Wed, 21 Dec 2005 18:11:43 +0000, Panther top-posted:

So, if the graph is important, then do the arithmetic on your pocket calculator, and draw the graph on a piece of paper.

Good Luck! Rich

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If you told us about the lab we might be able to figure out your final voltage, then you can scale V @ 5TC. Or, hand in your assignment in p.u.

Thanks but I've done that already (as in I know 5TCs will give me the voltage) what I meant was I dont know how to read it off the graph Winscope gives me.

Unforunately Winscope doesn't have any divisions (that I've seen) which tell me anything about the voltage. Its documentation is poor too.

Thanks anyway.

No that is impossible because I've done the practical and now I've to do the write up so there's no chance of me doing it again :(

I've

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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.

Time constant is resistance times capacitance Time in seconds, resistance in ohms, capacitance in farads.

AIUI that will scale the output reading.

if at some point the voltage was at a known level all other results will be proportionate to that reading.

Bye. Jasen

The write up at the link you posted says there is a point and click meter function. Can you use that to find the voltage?

Ed

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Give

You probably divide by Y1 (or Y2 if your signal was in input 2 and shown as trace 2).

OK so the bottom-most point is -3V and the top is +3 (or 2). I can understand this but what does the Y1 gain have to do with it? How will it affect what I read off?

Thanks

OK so the bottom-most point is -3V and the top is +3 (or 2). I can understand this but what does the Y1 gain have to do with it? How will it affect what I read off?

Thanks

is it? depends on your position and gain settings, plus various other factors outside the winscope program.

Its exactly the same as input gain on any old hardware scope. It sets the gain applied to the imcoming signal, just like a volume control.

If youre not understanding how to use winscope, then I think youre not understanding how to use oscilloscopes full stop. OSC251 is as simple as it gets.

NT