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intergator and rise time and fall time

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walters

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How do i measure Rise time ?

Do i set the time per division on the oscilloscope until the Ramp the diagonal line
fill the 8 divisions on the oscilloscope ?

So if the diagonal line goes aross the 8 divisions do i just count 8 divisions Multiple the time per division setting to get the Rise time?

example:

time per division setting is: 10 ms

8* 10ms = 80ms Rime time?


time per division setting is: 20 us

8* 20us = 160 us Rise time?
 

There are three basic definitions of rise and fall time.

1. Between the 10% and the 90% points. This is for most situations (where there is one dominant pole.)

2. Between the 20% and the 80% points. This is commonly used in high speed circuits where there are many hindrances to switching, such as the transistor limitations.

3. Taking the slope at the 50% point and extending it to the 0% and 100% levels.

The 0% and 100% levels stated above are the steady state amplitudes (high and low) that would exist with a very long time at each level.
 

Thanks for the information

how do i measure from 10% to 90% rise time?
do i measure it in time intervals?

I see the diagonal line on the oscilloscope where is 10% is it the first division ?
where is 20% because the rise time is a diagonal line how do i calucalate the
percentages of the diagonal line for 10%-90%?

Does the Rise time have a period ?

i need to know how to get 10%,20%,30%,etc -90% percentage values from a diagonal line the rise time?

i need to make a new chart for this stuff

whats the formula for this?
 

You will need to make the sweep slow enough to get the two (high and low) levels. Then measure the difference between them. Take the % of the range.

For example, if the two levels are -1 V and +2 V, 10% would be (-1 +0.3 V = -0.7 V) and 90% would be (-1 V + 2.7 V = +1.7 V) Locate these two points on the curve and find the time interval between them.
 

thanks

Can your pleases give me more examples to i can understand it more this is all new for me
 

i have a problem of knowing or getting the 10%,20%,30%,etc -90% percentage values from a diagonal line the rise time?

how do i get these percentages?
 

Take a look at this picture. Older scopes have those 10% and 90% dashed lines on their screen. What you do is adjust the vertical amplitude so that the waveform flat portions line up with the correct horizontal lines. Then you know exactly where 10% and 90% are and measure the rise time between those transition points.

On modern digital scopes, you have adjustable cursors (if not direct rise-time measurement) and adjust them for 10%, 90%, after you measure the amplitude. Then use the time cursors to read the rise time.
 

Thanks alot VVV for the pdf picture

Older scopes have those 10% and 90% dashed lines on their screen

Where are they i still don't know where the percentages are

I know where 0% and 100% is but i don't know where 10%-90% are
don't i have count the divisions and X by the time per divisions?

I need like a Old style oscilloscope display to help me out to "Guide" me better
because im just guessing really where 10%,20%,30%-90% are.

Is there a better way to have a % percentage "guide" made for me to help me out more
 

Well, yes, you do have to count the number of x divisions and multiply by time/div.

Sure you can make a chart for yourself, just establish the 0% and 100% lines and then draw on some transparent foil the corresponding 20%, 30%, etc. lines.
Then tape the foil over the scope screen.
When measuring on x, adjust the x-pos to make reading easier. For instance, shift the picture to the left until the 10% crossing point is at the start of the first division to the left.
 

Thanks VVV

The oscilloscope has 8 divisions

division is 0% ?
1st division is 10%
2nd divison is 20%
3rd division is 30%
4th division is 40%
5th division is 50%
6th division is 60%
7th division is 70%
8th division is 80%
9th ? 90%
10th ? 100%
 

No, that is not how it works.
If you can see those dashed lines on the screen, then the first solid line above the top one is 100% and the solid line below the bottom dashed line is 0%. (Usually it is the second solid line from the top and bottom that are 0% and 100%, i.e. you have 6 divisions for 100%, just like I drew them in the picture, but check to be sure).
That is all you need to do a 10% to 90% rise time measurement.

If you need other percentages, establish your own 100% scale and then divide it.
 

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