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Old 27th Jan 2023, 12:22 am   #1
erasmo0
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Default O_scope

Just Little question : I have connect an audio oscillator on o_scope and I see the sine...but if I change frequency by the knob of audio oscillator, the trace on the screen Is variable to left or to r right and too much Speed if increase the level of frequency on audio oscillator...why!?
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Old 27th Jan 2023, 3:10 am   #2
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Default Re: O_scope

It sounds like you need to learn about the triggering system for the oscilloscope's timebase. There is material on-line and also videos of explanations. Have a search around.

David
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Old 27th Jan 2023, 7:48 am   #3
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Default Re: O_scope

As David says it sounds like the trigger. Learning to "drive" your scope takes some time, also your scope might not have a good trigger, some scopes are better than others.

What scope is it? Some have various trigger settings, try playing with the control settings.

Andy.
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Old 27th Jan 2023, 12:00 pm   #4
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Default Re: O_scope

Guide to using an oscilloscope:
https://www.vintage-radio.net/forum/...7&postcount=52
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Old 28th Jan 2023, 12:59 am   #5
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Default Re: O_scope

Hi,mr david_andy_simon…o_scope is Gould-250 Made uk,ths for guide very useful,now i note trace in screen not much speed ( i have rotate knob Frequency audio oscillator about 60Hz ) and haven’t change the time knob o_scope…only to command knob in oscillator audio…i think because regulation is a about 60 Hz?
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Old 28th Jan 2023, 7:03 am   #6
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Default Re: O_scope

Quote:
Originally Posted by erasmo0 View Post
Hi,mr david_andy_simon…o_scope is Gould-250 Made uk,ths for guide very useful,now i note trace in screen not much speed ( i have rotate knob Frequency audio oscillator about 60Hz ) and haven’t change the time knob o_scope…only to command knob in oscillator audio…i think because regulation is a about 60 Hz?
If you accidentally synchronise the period of the oscillator with the period of the scope scan,which depends on the time base setting of the scope (or they fit into each other exactly - again by accident) then by accident the trace will appear stationary on the screen. Otherwise it will slowly, or rapidly, move left or right. The 'trigger' function stops this happening.

By the way, thanks for your neologism 'knob-o-scope'. I'm going to try to remember that one and use it.
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Old 28th Jan 2023, 10:28 am   #7
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Default Re: O_scope

You have a relatively modern, but very basic oscilloscope. The type used in schools and basic labs in universities. Pretty much an ideal instrument to learn on.

It's common for even fairly basic scopes to have two input channels. However, the CRT can only generate a single spot. So some trickery is needed.

You'll find switches to select channel 1 or channel 2 or alt or chop.

Channels could be numbered A and B or 1 and 2. I'll just use 1 and 2 for names.

Alt means that it runs the trace once for channel 1 then does it again for channel 2. If you're scanning fast enough, this is fine and it then works like a 2 channel oscilloscope. If your scans have to be slow, then you see one channel's trace being painted on the screen, then the other and flicker can be annoying.

Selecting chop starts a free-running oscillator switching between one trace and the other, so it looks like you have a two channel dual trace oscilloscope again, but with less flicker. Run the timebase faster and then you may start to see the chopping action between the two traces.

For what you're trying to do you only need one trace, so select channel 1 and life is simpler.

This puts channel 1 into Y-deflecting the spot on the screen.

As Mark has explained, a free running timebase can at various settings give a display which can appear fixed, but drifts off.

The solution is to have a timebase which is NOT free running. Old oscilloscopes took a sample of the signal and injected it into the timebase oscillator, relying on its tendency to lock on. This is not too reliable.

So the 'Triggered timebase' was invented (By Howard Vollum, founder of Tektronix) This is a more definite system.

You should have switches to select which channel you trigger from (or from a sample of mains) then a switch for AC or DC coupling (AC should be fine to start with) and a level control to set the trigger threshold, and a +/- switch to select whether to trigger when crossing the threshold in a +ve going or a -ve going direction.

There is likely to be a switch to set the trigger running to 'normal' or 'auto'

Normal makes the timebase halt waiting for triggering to occur. No triggers and you get no traces. You have to fiddle with the trigger controls until you find a trace.

Auto makes the timevase wait for a trigger, but if one doesn't happen for well over the full scan time, it fires on off anyway. This can give you unwanted triggeredd scans when you don't want them, but those scans give you clues about how to set the trigger controls to get them working.

David
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Old 28th Jan 2023, 12:19 pm   #8
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Default Re: O_scope

Operation section of the OS250 user manual:-

Gould OS250 Operation.pdf

Full user/service manual here: <LINK>

Cheers
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Old 29th Jan 2023, 2:31 am   #9
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Default Re: O_scope

So it was the trigger that must have captured the signal of the line ... in fact I had randomly set the settings of the o_scope ... Mark's answer was essential and together with the basics that David gave me on the operation of the o_scope, it gave me more security in its use, really thank you also for the "Link" with the technical manual of my Gould
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Old 29th Jan 2023, 2:45 am   #10
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Default Re: O_scope

Once you're triggering, you can move the time/division controls around and you see the waveform stretch and shrink, pinned at the lefy edge of the screen, you shouldn't get a picture that just drifts across the screen.

Play around with the trigger controls and tou'll see that they set what the signal has to be doing at the left edge of the screen, where and when the timebase is released to run.

It all becomes comfortable and natural as you get used to it.

David
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Old 2nd Feb 2023, 1:03 am   #11
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Default Re: O_scope

It all becomes comfortable and natural as you get used to it. 👍
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