|Portable USB Scope|
The USB soundcard has a mono microphone input, and stereo output. This design is for a one channel scope, with an output for use as a function generator. This device is small enough to carry in your laptop bag, and can be used to test equipment from line level up to speaker level audio.
The protection circuit ensures voltage at the soundcard input is clipped at 1.2Vp-p.
Circuit will mount nicely on the back of a 16mm potentiometer.
Probe Input Circuit
Mounted on a small piece of veroboard.
USB Sound Card
These devices are available on eBay for less than two dollars. Mono microphone input, Stereo output.
The USB-A connnector and 3.5mm sockets were removed, so that wires can be soldered directly to the board.
Sound card is wired to probe input circuit board.
Output control circuit is wired point-to-point.
USB cable is soldered directly to sound card. Heatshrink is added to prevent shorting.
BNC connectors are used to connect test probes.
6.5mm socket for use with audio test leads.
Banana socket to connect ground lead.
|Visual Analyser Software|
It is available for free download here: http://www.sillanumsoft.org/download.htm
Visual Analyser uses your USB soundcard to display oscilloscope traces, as well as frequency spectrum. However, the soundcard must first be set up correctly.
Right click on your volume control icon in the task bar.
Select "Recording Devices".
Choose the USB soundcard input
Select the "Custom" tab.
Un-check AGC (automated gain control).
Select "Levels" tab.
Increase microphone to 100%.
Visual Analyser is now ready to use.
This device is useful for inputting a sine tone into audio equipment, and testing the output. The amplitude control knob of the input circuit allows testing of line level audio (1V), and up to speaker level audio (100V).
WARNING: UNIT GROUND CONNECTS TO PC GROUND.
Always connect the ground clip of the device to the chassis of the equipment to be tested. Using the ground clip as a probe will short live circuits to ground through your test device and PC (This goes for any oscilloscope that is not isolated from ground).
NOT FOR USE WITH MAINS A.C.