Shutter tester using an oscilloscope

micromoogman

micromoogman

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Hi
I have an oscilloscpe that I found cheap in a charity shop. It seems to work. I thought I might use it as a shutter tester. Could someone provide me with a scheme on how it would be set up? I need a photo cell obviously and a battery I guess, a light source of some kind... Well, I'm not use to handle these machines so an overall explanation would be very helpful.

Regards Jonas
 
Unfortunately, all I have is a digital oscilloscope, but it's nearly the same procedure. You need to be sure that the light detector responds faster than the shutter speed you are testing. Here is my procedure:
  1. Set the sample rate to 1000 samples per second for 10 seconds:
    samplerate.jpg


  2. Shine a light directly on the detector to determine the maximum value:
    setup.jpg


  3. Block the light detector with the shutter to determine the minimum light:
    minimum.jpg


  4. Open the shutter to determine the maximum light:
    maximum.jpg


  5. Begin sampling and trip the shutter during the sample period:
    sampling.jpg


  6. Review the data.
    data.jpg


  7. Measure from the "halfheight" of the left side horizontally to the "halfheight" on the right side. Here is the measurement for the test shown above. The shutter was set to 1/4 second, and the data shows actual time the shutter was open to be only 2% longer, or 0.255 seconds:
    quartersec072712.gif



The main difference in doing this with an analog 'scope, is that you will need to note on a scale, in real time, where the edges of the maximum data fall. They used to have Polaroid film made for recording oscilloscope traces with a special camera. You will likely need to write it down, or have a caliper ready when you do the sample.
 
If it is an old plain analog scope you won't be able to use for shutter testing unfortunately:( The scope needs to have a memory of some kind for this to work. Now, some old analog scopes had this memory function but they were rare and expensive.

Why is this? The curve on an oscilloscope sweeps from left to right. For a pattern to be stable the pattern has to repeat on each sweep. The shutter goes off only once and unless you manage to see that single sweep you will only see the normal left-right sweep again.

I use an old HP digital scope (with memory) for this and the setup uses a BPX43 phototransistor as detector, with a 10k resistor from collector to +9V. Ground is connected to the emitter and the signal to the scope is taken between collector and emitter of the phototransistor. A table lamp acts as illuminator.
 
emjo said:
If it is an old plain analog scope you won't be able to use for shutter testing unfortunately:( The scope needs to have a memory of some kind for this to work. Now, some old analog scopes had this memory function but they were rare and expensive.

Why is this? The curve on an oscilloscope sweeps from left to right. For a pattern to be stable the pattern has to repeat on each sweep. The shutter goes off only once and unless you manage to see that single sweep you will only see the normal left-right sweep again.

I use an old HP digital scope (with memory) for this and the setup uses a BPX43 phototransistor as detector, with a 10k resistor from collector to +9V. Ground is connected to the emitter and the signal to the scope is taken between collector and emitter of the phototransistor. A table lamp acts as illuminator.
Click to expand...

Ah, what a pity. It's an old analog oscilloscope. I will check if it has that memory function. I will try that sound card trick instead. I guess it will give about the same results.

Thank you all for the help anyhow!
 
If you have a digital camera you can set it to B and expose a trace and study that on the pc. At least a use for a digital camera :D

I use a Toshiba TORX digital audio receiver. Together with a piece of toslink cable I can check at different places accross the shutter.
 
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