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Oscilloscope

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yasir_ali

New Member
hey! every one, is there any trick or software that i just have 2 prob out from my PC and then i can check the output wave form of any circuit. in short, i'm talking about a pc Oscilloscope. is there any? please tel me know.
Thanks
 

Reloadron

Well-Known Member
Most Helpful Member
hey! every one, is there any trick or software that i just have 2 prob out from my PC and then i can check the output wave form of any circuit. in short, i'm talking about a pc Oscilloscope. is there any? please tel me know.
Thanks

The short answer is no. The long answer is yes. Using a PC as a scope requires the addition of external hardware and install of some software. Can you just somehow connect a few probes to a PC and make it work like an oscilloscope? Nope.

Ron
 

dougy83

Well-Known Member
You can use the PC soundcard as a 'scope. Caveats might be that the bandwidth is limited to maybe 20 Hz - 20 kHz and the input voltage is line level; also the frequency response is not flat (you can compensate for this through calibration). A nice scope program may be found here Soundcard Scope
 
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yasir_ali

New Member
Hey dougy83! i've downloaded the soundCard Scope.
2 problems:
1- can't the input voltage to the Sound Scop(Sound card) greater then ±0.7v?
2-how get a private lisence i'm a student.?
 

dougy83

Well-Known Member
1- can't the input voltage to the Sound Scop(Sound card) greater then ±0.7v?
Yep, "line level" is around that. Read further down his page and you'll see he recommends using resistor dividers to reduce larger voltages to this level. He also recommends using shunt diodes to stop you overloading your soundcard.

2-how get a private lisence i'm a student.?
You can either pay AU$18 (it's a donation), or not. If you can't afford it, don't pay - the software is apparently free for students.
 

Ubergeek63

Well-Known Member
The short answer is no. The long answer is yes. Using a PC as a scope requires the addition of external hardware and install of some software. Can you just somehow connect a few probes to a PC and make it work like an oscilloscope? Nope.

Ron
ummm... yep

there is software that allows the use of the audio hardware as a scope. it is, of course, limited to the capabilities of the installed audio hardware ... nice for demos and Lissajous, but only good for maybe 10KHz, and possably not below 100Hz .. and there is a free one

https://www.zeitnitz.de/Christian/scope_en

dan
 
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yasir_ali

New Member
hey! i forgot the concept of SHUNT DIODE. I think a parallel connected diode is called a shunt diode. am i correct.?
 

Space Varmint

New Member
Can you tell me the purose of the shunt diode and how this shunt diode protects the Circuits from any demage.?

I believe it tends to send over voltage spikes to ground or limits them. Don't take my word for it though. I'm digging way back in my memory banks...lol :)
 

Reloadron

Well-Known Member
Most Helpful Member
Just off the cuff the best example of a "shunt diode" would be like when a diode is placed (reverse bias) across a DC relay coil.

One very common practice is to simply shunt the coil with a general
purpose diode, placing the diode to block the source voltage and conduct
with the reverse polarity of the coil induced voltage. This provides a path
for the current flowing in the deenergized coil to be externally shunted
back into the coil, limiting the magnitude of coil induced voltage to the
forward drop of the diode, which the coil current, and resulting magnetic
flux, slowly decay.

I have also heard the term used as n series or parallel shunt diode detectors which is another animal.

Ron
 

dougy83

Well-Known Member
There seems to be some confusion. Attached is how the diodes would be wired up. Top diagram (2 diodes total) limits the voltage to the soundcard to ~+/-0.7V, the lower (4 diodes) ~+/-1.4V.

prot.gif

The resistors should be selected to suit the input voltage range.
 
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Reloadron

Well-Known Member
Most Helpful Member
That is a circuit I always referred to as a Diode Clamp or Clipper circuit. The diodes will clip or clamp the incoming signal level to the forward voltage drop of the diodes or about .6 to .7 volt so if you have two in series about 1.2 to 1.4 volts. The problem is if you run for example a sine wave into it the waveform is clipped or clamped.

Ron
 

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dougy83

Well-Known Member
The problem is if you run for example a sine wave into it the waveform is clipped or clamped.
The same thing happens if you don't use the diode (the ADC maxes out) - except that it's rumoured that the soundcard doesn't enjoy it.
 

Reloadron

Well-Known Member
Most Helpful Member
The same thing happens if you don't use the diode (the ADC maxes out) - except that it's rumoured that the soundcard doesn't enjoy it.

I wouldn't be happy if I was the sound card.

I guess if someone really wanted to take the route of using software to use a sound card as a scope it would work but just be so limited. You could build a front end to attenuate etc but you can only take it so far. There are no shortage of USB scopes out there ranging in price from a few hundred (USD) to a few thousand dollars (USD).

Another trick that works well is to use a cheap data acquisition starter kit like this one which is cheap because it is serial port and limited but with the included software works pretty well in scope mode and for data logging. There are countless others out there.

Then too, if someone had the urge they could likely add a front end to a PIC and write the software I guess.

Anyway, using the sound card and the mentioned software would likely make for a inexpensive basic scope if a front end was built to act as an attenuator / amplifier stage.

Ron
 
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