.56 seconds and .28 seconds time measurement on an analog oscilloscope

[Billy Mayo]

.56 seconds and .28 seconds time measurement on an analog oscilloscope

I had to do these time measurements at work using an analog oscilloscope

All I could get was a Dot moving up and down , is this because the pulse waveform is to fast or to slow?

I had to use a storage analog oscilloscope and turn the moving Dot into a stored waveform

The Oscilloscope turned the moving DOT swinging from +10 to 0 into a Pulse square waveform , how did it do that?

Without using a Storage analog oscilloscope , how do you use a analog oscilloscope to measure the One time and Period of a waveform that is .28 seconds?

 

[Billy Mayo]

The Service manual at my work date back to the 60's and have pictures of the pulse waveforms at .28 seconds or .10 seconds , how did they use an analog oscilloscope and measure the ON time and Period of the waveform when all I can see is a moving swing DOT

I had to use an storage analog oscilloscope to turn the moving swinging DOT into a square waveform , but these service manuals are in the 60's , so how did they measure these .20 second square waveforms?

 

[Pommie]

They probably used a camera with the shutter speed set to the period of the trace.

The way to do it manually is to get the waveform in a fixed position by getting it to trigger at the same time each pass. Then move it horizontal until the up movement is on a line and watch where the down movement occurs.

Mike.

 

[Billy Mayo]

I moved the Time per division in all positions , all I could get was a DOT swinging up and down

The Storage O-scope was the same problem too, but I had to STORE the DOT and it turned the swinging DOT into a square waveform train

 

[Pommie]

If you set the scope to trigger on the channel you are looking at then the transitions position on the screen should stay stationary. You can then see the time between transitions. Can you get the trigger to be consistent?

Mike.

 

[Billy Mayo]

The Trigger is constant , but the waveform is .23 seconds, so the O-scope doesn't Display a squarewaveform, it displays a Moving Swinging Dot

The Only way to get it to Display it as a squarewaveform was, I had to use a storage O-scope to Display the .23 second as a squarewaveform

I moved the trigger knob in both direction , it has nothing to do with the trigger

It's the fact that the analog O-scope can't "DISPLAY" a .23 second as a waveform unless you use a storage O-scope

 

[Pommie]

If you set the time scale to 0.1s=S/div then it will take the dot approx 1 second to get across the screen. If the trace always starts on a positive transition then the trace will be the same every time. You can then see where it moves up/down. You don't need to see a square wave, just where it moves up/down. The way you get it to trigger in the right position is by playing with the trigger values.

BTW, an analog scope can't "display" a 1kHz waveform but just a jumpy dot as you describe. However, your eyes can't see it at that speed so it appears as a square wave. The picture is in your head not on the scope. (For the pedants on here, I know the phosphorous helps but the point is still valid - pun intended).

Mike.

 

[Billy Mayo]

Yes I see where the DOT moves up and down

But how do you measure the ON TIME and PERIOD? if you can't see it or it's displayed on the O-Scope?

It's hard to measure the ON TIME and PERIOD when the DOT is moving up and down

 

[Jaguarjoe]

If you set the time scale to 0.1s=S/div then it will take the dot approx 1 second to get across the screen. If the trace always starts on a positive transition then the trace will be the same every time. You can then see where it moves up/down. You don't need to see a square wave, just where it moves up/down. The way you get it to trigger in the right position is by playing with the trigger values.

BTW, an analog scope can't "display" a 1kHz waveform but just a jumpy dot as you describe. However, your eyes can't see it at that speed so it appears as a square wave. The picture is in your head not on the scope. (For the pedants on here, I know the phosphorous helps but the point is still valid - pun intended).

Mike.

FWIW, it may not be important but analog sweeps are ~3% accurate.

 

[rumpfy]

Billy,
It sounds to me like your CRO was not sweeping in the horizontal direction. In general, if you disconnect the input to a CRO you will see a horizontal line. Then, when the input signal is connected to the vertical amplifier, the signal waveform will be displayed.
The generation or initiation of the horizontal sweep is done by 'triggering'. ALL cro's have triggering controls and my experience is that use of the triggering system is the most misunderstood part of using a cro.
I my view the only CRO ever to have had decent triggering arrangement was the Tektronix. My Tek 564 still goes well. I love it!!.

 

[atferrari]

Sweeping is not working if all what you actually see is a trace going up and down and not moving to the right.
BTW, are you sure you selected the right timebase? Isn't the scope in the XY mode?

You started talking about 0.28 and then 0.23. (?)

 

[Billy Mayo]

when you see signals or waveforms that are a travelling DOT, are these really SLOW waveforms or Low frequency waveforms?

How do you see a Continuous waveform when you're measuring waveforms that are a Travelling DOT?

At Slow Sweep Speeds on the O-scope, What kind of waveforms are these? are they short?, long? low frequency?

I have tried single sweep and I couldn't get the it to CATCH or lOCK onto the waveform to give a Travelling DOT or a continuous waveform

A .28 second waveform? how does a Electronic Tech know how to calculate on the SWEEP SPEED on the O-scope what the setting should be? to give a continuous waveform?

 

[Dean Huster]

Mike is right on. But triggering may be your problem. With that slow of a signal, you vertical amplifier must be DC coupled, not AC. And the triggering/sweep controls will have to be set for DC coupling and NORMal, not AUTOmatic.

 

[crutschow]

Years ago when I had to view a low frequency wave on a standard analog scope I used a scope hood to block out ambient light (or turn off the ambient lights) and then reduce the trace brightness to give a just visible trace. The low level phosphor decay time was then generally long enough to see the whole trace similar to a storage scope, even at a slow sweep speed. You might try that.

 

[Billy Mayo]

how do u calculate the o-scope sweep time when you know the waveforms period time?

.62 seconds is the time period, how do i calculate the o-scopes sweep time? instead im just guessing

 

[crutschow]

how do u calculate the o-scope sweep time when you know the waveforms period time?

.62 seconds is the time period, how do i calculate the o-scopes sweep time? instead im just guessing

The sweep speed is given in time/division. So if your scope has 10 horizontal divisions (grid) and you want the total sweep to take 1 second then you would set the sweep speed to 0.1s (100ms) / div.

 

[Billy Mayo]

To measure .28 seconds you need a sweep speed of .20 seconds to see it Display a waveform to measure it
My 0-scope only goes to .5 seconds

500milliseconds = 2hz , What is the formula to calculate the sweep speed?

280milliseconds = 3.57hz, What is the formula to calculate the sweep speed?

I know the Period time and frequency but I don't know what sweep speed I should use , I'm just moving the sweep speed knob back and forth until i get a waveform but i'm guessing

1 millisecond = 1khz, But how do I calculate what the sweep speed should be?

Example:
The Formula should be waveform Period Time ( which is 1 millisecond) X or divided by what ? = Sweep Speed on O-scope

 

[Reloadron]

There is no formula per se. You generally want to see as much of the signal as possible. If I want to view a 500 mS pulse I would use a sweep speed of .1 Sec / Div and my pulse should occupy about 5 divisions horizontally. I could use 50 mS / Div but then my signal would occupy all 10 of my horizontal divisions and if my pulse exceeds 500 mSec I am outside my measuring grid lines.

Actually for slow signals an old analog scope isn't the best choice. A counter would be the better choice but when you don't have a counter or older analog storage scope or new digital scope then you work with what you have. I would set things up as Carl mentioned earlier:

Years ago when I had to view a low frequency wave on a standard analog scope I used a scope hood to block out ambient light (or turn off the ambient lights) and then reduce the trace brightness to give a just visible trace. The low level phosphor decay time was then generally long enough to see the whole trace similar to a storage scope, even at a slow sweep speed. You might try that.

Anyway, there is no "formula" for determining the sweep speed.

Ron

 

[Billy Mayo]

If I want to view a 500 mS pulse I would use a sweep speed of .1 Sec / Div and my pulse should occupy about 5 divisions horizontally. I could use 50 mS / Div but then my signal would occupy all 10 of my horizontal division

s

Well how did you calculate this tho? 500mS X 10 divisons on the 0-scope = .1 sec sweep speed?

 

[rumpfy]

billy,
Have a look at this post.

www.electro-tech-online.com/threads/tenma-72-3055-oscilloscope-questions.136256/page-2#post-1149321

In my post #29, there is a reference to a U tube video.
Have a look at the video and then come back with questions.
I have to say that reading your reaction to the comments, that you seem to be completely unfamiliar with the oscilloscope and what it displays and how to work it. After seeing the video you may be better placed to understand many of the comments here. AND, a photo of the scope you were using, OR, a make and model number would be good.
Hope this helps.