irregular tigger pulse why?

[danny davis]

There is 20 trigger pulse every 50ms

Each Trigger pulse is suppost to be 15us apart from each other

The problem is that every pulse is different intervals from each other

Some are 20 us part , 14 us part , 18 us , 16 us down the timeline

What type of problem is this called? and what causes this?

So the pulse train is irregular

 

[CocaCola]

A timing problem...

 

[danny davis]

but what cause irregular timing problems?

 

[danny davis]

Yes its a time problem , but what is this called that the intervals are not constant and they change?

 

[(*steve*)]

What is generating the trigger pulses?

At some point (very soon) we're going to say "we can't help you without a schematic"

 

[CocaCola]

At some point (very soon) we're going to say "we can't help you without a schematic"

From garnishing previous post, you won't get any additional information about the circuit but he will continue to push for that single de facto answer for the question that doesn't have one...

what cause irregular timing problems?

Do you Google?

 

[danny davis]

I'm not sure myself what is generating the pulses

But mostly a clock or oscillator circuit will generator a constant pulse train

I'm just not sure how each pulse in the pulse train can have different time internals

Is it the clock circuit? or oscillator circuit?

 

[CocaCola]

I'm not sure myself what is generating the pulses

Don't you think that would be a good thing to find out and use as a starting point for your diagnosis?

But mostly a clock or oscillator circuit will generator a constant pulse train

Possibility, when they are designed and working properly...

I'm just not sure how each pulse in the pulse train can have different time internals

It's not working properly, something is causing interference/failure/shift etc, or it's not designed to...

Is it the clock circuit? or oscillator circuit?

You tell us...

Did you Google?

 

[danny davis]

This is the QC test I been doing at work

To measure Digital Pulses using an digital oscilloscope

To Measure Pulse Width:
1.) You take the cursors and line up the leading edge and falling edge of the pulse to measure the pulse width
2.) The Problem with the boards are that the Starting pulse, its pulse width is not the same pulse width as the other channels on the oscilloscope, cause I'm measuring the same boards just on different channels, But what's weird is that the starting pulse/trigger has a different pulse width compared to the other PCB's
3.) Not sure what causes this problem?

To Measure Time Interval
1.) You take the cursors and line up the falling edge of pulse#1 and line up the other cursor with the leading edge of pulse#2
2.) The Problem with the boards at work is that each pulse is suppost to have a constant 15us time interval between the next pulse, but what I am getting is 13us, 16us, 18us, 12us etc so each pulse interval is different in the pulse train

To Measure Pulse Lag? or offset time?
1.) Pulse train#2 is lagging Pulse Train#1
2.) I measure the Lag time or offset time or time interval between Pulse Train#2 and pulse train#1
3.) The boards at my work have 4 pulse waveforms, they are suppost to start all at the same time in sync, but they don't. Either One or Two waveforms have a Lag time so I have to measure that.

What other Tests Can I do please?

 

[duke37]

Is the digital scope fast enough to resolve the time accurately?
Try an analogue scope.

 

[danny davis]

we are using SINGLE trigger mode is that right?

And then zooming in on the waveforms

 

[danny davis]

Also another Problem I'm getting on the oscilloscope is that it cuts off the beginning part of the squarewaveform pulsewidth

a trigger display problem

1.) I'm using Single mode
2.) Positive Triggering

It cuts off the beginning part and i tried using the horizontal adjust and its still cuts off on the left of the screen

How can I see it from the beginning?

 

[(*steve*)]

You need yo use an oscilloscope that can display the signal before the trigger input.

This will dictate the use of either a delay line or a digital scope.

Alternatively, you need a trigger that occurs earlier.

 

[danny davis]

Do i have to use the HOLDOFF knob or Delay trigger knob?

 

[danny davis]

You need yo use an oscilloscope that can display the signal before the trigger input.

Most of the scopes i use have a trigger know but it only sets the amplitude/voltage of the trigger threshold

I can't find where it sets the trigger earlier or before the trigger input

 

[(*steve*)]

The answer is to RTFM

 

[danny davis]

Does the Hold off knob on the oscilloscope adjust the beginning trigger point?

At work they have a digital storage oscilloscope

I'm not sure what they are used for as in , what kind of measurements you would make from having waveform stored

I press auto trigger so the oscilloscope runs in real time, and then I hit the single trigger and I guess it snap shots the waveform?

I'm not sure where to adjust how long the snap shot is to take, I don't think this oscilloscope has a setting where u can adjust how long of the time cycles you want , it seems to be a FIXED setting

At work they want me to scroll through the digital signals to check for
1.) glitches
2.) Pulse Width
3.) Time Intervals

What else can I check for?

How do you guys use a Storage oscilloscope and what u use it for?

 

[CocaCola]

How do you guys use a Storage oscilloscope and what u use it for?

Are you afraid of Google?

I Don't Bite Back

 

[danny davis]

ya but i want to know how u guys used a storage scope and what u did with it

 

[foTONICS]

I'm just not sure how each pulse in the pulse train can have different time internals

Maybe it's data being transferred, like this

http://en.wikipedia.org/wiki/Manchester_code