I am looking for a good PC based oscilloscope/spectrum analyser software that is freeware or shareware.
Any good ones out there that are worth trying ? Something that uses the sound card would be great, but if there is an external acquisition unit that could be built or bought for cheap that is fine too.
Any good ones out there that are worth trying ? Something that uses the sound card would be great, but if there is an external acquisition unit that could be built or bought for cheap that is fine too.
If you're just looking for a cheap non-recording 'scope, make sure you check the local classifieds, ham swap meets, etc.
My first scope was a 35 year old model I picked up (along with a bunch of spare tubes and a 4.5" needle bench multimeter) for twenty bucks. It was made for colour television repairmen, so although the bandwidth wasn't written on it, I'm pretty sure it's good to at least 4.7 MHz.
The only problem with old 'scopes is that they're full of old capacitors and dirty knobs. Mine still has a ~60Hz waggle that is about 10mV high. No big deal, as long as I have a good strong signal (i.e. audio line level) to beat it into submission with.
I have a new 'scope now (120Mhz Phillips) courtesy of my dad, but I haven't had to use it yet. Fixed everything on my "must fix" list with the old 'scope, but I'm sure the new one will come in handy when I build my chip amp next month.. or when I finally get that other formerly -stereo-now-mono amp in my living room cracked open.
Wes
My first scope was a 35 year old model I picked up (along with a bunch of spare tubes and a 4.5" needle bench multimeter) for twenty bucks. It was made for colour television repairmen, so although the bandwidth wasn't written on it, I'm pretty sure it's good to at least 4.7 MHz.
The only problem with old 'scopes is that they're full of old capacitors and dirty knobs. Mine still has a ~60Hz waggle that is about 10mV high. No big deal, as long as I have a good strong signal (i.e. audio line level) to beat it into submission with.
I have a new 'scope now (120Mhz Phillips) courtesy of my dad, but I haven't had to use it yet. Fixed everything on my "must fix" list with the old 'scope, but I'm sure the new one will come in handy when I build my chip amp next month.. or when I finally get that other formerly -stereo-now-mono amp in my living room cracked open.
Wes
I will check out the audiotester.
Has anybody used any of these -
http://www.dazyweblabs.com/shannonsoft/page3.html
Has anybody used any of these -
http://www.dazyweblabs.com/shannonsoft/page3.html
All the soundcard based o'scopes or FFTs are restricted in their bandwidth due to the sample rate of the soundcard, which is generally around 44KHz - 48KHz so you cannot do 10K THD or square waves which require 100KHz min and pref >>1MHz.
A 20MHz analogue CRO is a bare minimum for viewing parasitics on square waves.
Cheers,
Greg
A 20MHz analogue CRO is a bare minimum for viewing parasitics on square waves.
Cheers,
Greg
See this thread:
http://www.diyhifi.org/forums/viewtopic.php?t=302
I find this software pretty good for signals frequencies up to the soundcard limits.
You'll not see if an amp oscillates though, but it's useful anyway.
Tino
http://www.diyhifi.org/forums/viewtopic.php?t=302
I find this software pretty good for signals frequencies up to the soundcard limits.
You'll not see if an amp oscillates though, but it's useful anyway.
Tino
I recently ran across this:
http://www.esi-pro.com/viewProduct.php?pid=43&page=1
Appearently the 24/192 capability is for both in- and out-put and is done in gardware unlike some others. I googled for reviews and at least one reported <.001% THD+N using thr RightMark loop back test. It's not all one would want but should resilve out to the 7th harmonic for a 10kHz test. I've seen street prices as low as $125. This doesn't refute what was written above, but it indicates that the limits are not quite as bad a formerly.
Agree. Fortunately you can get this on E-bay pretty cheap.
The cheapest spectum analyser (I know of) that reads in Mhz, that I know, is the Velleman (for some reason ElectronixExpress carries it much cheaper than anyone else). Unfortunately, it only has 8-bit resolution which limits the lowest distortion figures youi can measure without bulding some of your own external fixtures.
It looks like one really need at least 2 instruments at6 this point in time. Even the PicoTech 16-bit resolution (which is beyond my current budget) has bandwidthy limits.
percy said:
How about this one ?
TrueRTA:
http://www.trueaudio.com/rta_abt1.htm
They have a couple of versions, the basic one is free but appears to cover your needs.
Best regards,
João Pedro
Re: Laptops
Since most soundcards work with signals around 1 V (rms) ,maximum, it is a extremely good idea to build an interface so you can measure signals of a couple hundred volts without blowing our soundcard's circuitry. This is only for LINE IN, not mic input !! Try to find information on your soundcard to make sure. Mine is an old Sound Blaster Live.
I built this interface using a basic voltage divider, protected by 2 diodes in series in anti-parellel, so amplitude never exceeds 1.3 V even if you connect a high voltage signal in the wrong point of the divider. Use low noise resistors.
You can build a probe with a shielded cable with some sort of clamping connector.
It works nice ! But it is a good idea to calibrate your signal with a signal of known amplitude.
I hope that helps.
João Pedro
lgreen said:
Since most soundcards work with signals around 1 V (rms) ,maximum, it is a extremely good idea to build an interface so you can measure signals of a couple hundred volts without blowing our soundcard's circuitry. This is only for LINE IN, not mic input !! Try to find information on your soundcard to make sure. Mine is an old Sound Blaster Live.
I built this interface using a basic voltage divider, protected by 2 diodes in series in anti-parellel, so amplitude never exceeds 1.3 V even if you connect a high voltage signal in the wrong point of the divider. Use low noise resistors.
You can build a probe with a shielded cable with some sort of clamping connector.
It works nice ! But it is a good idea to calibrate your signal with a signal of known amplitude.
I hope that helps.
João Pedro
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