Electronic Circuits and Projects Forum

Originally Posted by ljcox

Alternatively, use an analogue storage scope.

Thanks

One of my friends has an analog storage oscilloscope like this HITACHI 20MHz VC-6020 DIGITAL STORAGE OSCILLOSCOPE 2CH - eBay (item 310234571675 end time Jan-12-11 23:24:58 PST)

Do you think it will be able to display the square wave nicely? Except for the plotter output, the only other thing it has (and my scope doesn't have) is a HOLD button.

Originally Posted by ljcox

I'm not familiar with that scope, but if it can store a waveform, then it should be able to display your signal.

I tried. Same problem. The HOLD button only helps to retain the screen display at the particular moment the button is pressed. It does not have "memory" like a digital oscilloscope where I can use cursor to scroll back and forth the waveform and examine the various data points. Not sure if the PLOTTER output could have helped - I did not have the equipment to try.

The quality of the camera makes a lot of difference. My phd (press here dummy) camera decides when it has seen enough light and closes the shutter. End of list.

A better quality of the species "modern digital camera" will allow all kinds of adjustments, just like the old 35mm film cameras. Speed dominant, shutter opening dominant, plus and minus F-stops. Gosh, the words I have forgotten are making me look stupid. Anyway, you get the idea. Good camera = good results.

Years ago Tektronix manufactured a line of scope cameras. Some used roll film and some used Polaroid film packs. They attached directly to the CRT face and for their day worked well.

You turned up the graticule illumination and set the scope for single sweep. Then you opened the shutter and initiated a trigger for the scope. Once complete you close the shutter and in the case of Polaroid film pulled the tab and removed the exposed film. Wait about 60 seconds and peel the film backing off to reveal your lovely black and white image. For their time they were actually pretty cool and very useful devices. Today good luck finding film for one.

I guess if I wanted to capture a scope image with a slow rep rate today I would use a digital camera with a good choice of manual settings. That would include a camera with the mentioned "B" or Bulb setting for the shutter. Set up the focus and F Stop and then in the dark open the shutter. Set the scope for single sweep and remote externally trigger the scope. Once the trace is complete close the shutter and see what you have. You will need a good digital camera with a wide range of manual control. You will need to play around with the scope intensity and graticule illumination.

Ron