PCLab version 1.0 Trial
PCLab makes your soundcard to work as a signal generator and
oscilloscope. PCLab requires Win98 or later with DirectX9 installed.
IMPORTANT NOTE 1: Connecting
devices to your computer may damage or destroy the device and/or
computer. The authot takes no responsibility for any such damage or its
consequences. To decrease the risk of connecting the computer to the
measured devices, we recommend that you build a separator. Its scheme
is included in the software package in the file separator.png. However, incorrect use
of the separator may in some cases increase the risk of such damage to
the device.
IMPORTANT NOTE 2: Before using
this program, please turn off any effects you have enabled on your
soundcard (like 3D stereo enhancement). They are applied by Windows to
any sound from any application and may lead to serious distortion of
the signal generated by Signal generator or viewed by Oscilloscope.
IMPORTANT NOTE 3: There is a
full version of PCLab which is two-channel and is not limited to just
one sweep time. It costs 20USD plus shipping and handling.
You can get it from www.bolekvrany.cz.
Signal Genearator
Signal generator can generate sinus, rectangular or saw signal. The
maximum frequency is 22050Hz, which is the maximum frequency satisfying
the Nyquist theorem at 44100 samples per second.
The quality of the signal is limited by your soundcard. First of all,
the bandwith of the soundcard is quite limited. This means that sinus
is quite good to high frequencies, but rectangular and saw profiles get
distorted early because of the lack of higher harmonics. Second, your
sound card may have capacitors at output. They filter out the DC
component which means that the offset settings is unusable.
To start working with the program, go to Tools->Settings and select
the required output device. Select sinus signal, set maximum loudness
at your sound card and maximum amplitude in signal generator. Take an
osciloscope and measure the maximum voltage in your signal. Fill in
this value to the "Volts in maximum" fields of the Tools->Settings
dialog. This way signal generator gets calibrated, so that the
displayed voltage corresponds to the real voltage. If you do not want
to do it (or cannot do it), you need not. However, the correspondence
between the displayed and real amplitude is then arbitrary. Also please
note that the measured peak voltage may depend on frequency. In order
for this correspondence to last between runs of this program, you must
use the same Windows volume settings for each run.
Oscilloscope
You can use Oscilloscope to view various signals on the input of your
sound card. The maximum frequency is approx. 22050Hz, which is the
maximum frequency satisfying the Nyquist theorem at 44100 samples per
second. Please note that the line-in input of your sound card is
usually inhibited. To enabled it, go to the Windows volume settings and
enable the extarnal source.
The quality of the signal is limited by your soundcard. First of all,
the bandwith of the soundcard is quite limited. This means that sinus
is quite good to high frequencies, but rectangular and saw profiles get
distorted early because of the lack of higher harmonics. Second, your
sound card may have capacitors at input. They filter out the DC
component which means that you may not be able to see the DC offset,
just the AC signal modulated on it.
To start working with the program, go to Tools->Settings and select
the required input device. Connect sinusn signal of known amplitude to
the input. Set its amplitude to the maximum value at which the
displayed signal is yet not cut off. Fill in this value to the "Volts
in maximum" fields of the Tools->Settings dialog. This way the
oscilloscope gets calibrated, so that the displayed voltage corresponds
to the real voltage. If you do not want to do it (or cannot do it), you
need not. However, the correspondence between the displayed and real
amplitude is then arbitrary. Also please note that the measured peak
voltage may depend on frequency. In order for this correspondence to
last between runs of this program, you must use the same Windows volume
settings for each run.
If in memory mode, the oscilloscope stores data until explicitly cleared
by Tools->Clear or by changing the timebase. If you let the memory mode
run for a long time, oscilloscope may use all available memory.