irregular tigger pulse why?

[walters]

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

 

[gutierrez]

What's their source?

 

[enjunear]

What is creating the pulse train? A piece of test equipment (function generator, etc), a microcontroller, or other?

 

[walters]

either digital chips or a microcontroller

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

 

[walters]

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?

 

[D.A.(Tony)Stewart]

It's called signal to noise ratio problem. Is it bad design, bad layout or bad parts?
A bad design may have inadequate filtering or detector offset and or hysteresis. It can have supply noise, crosstalk or digital noise on the analog ground.
How important is it that it be fixed? Where are your Test and PRoduct Engineers?

 

[enjunear]

either digital chips or a microcontroller

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

It's called.... "a problem" :wink:

It sounds like you are performing the test correctly, but I'm not sure what you want to know. You've described the issues well (irregular/incorrect pulse width, irregular pulse separation, and irregular pulse-train spacing), so I'd use those terms/phrases to describe them. If there is another design engineer, then it's time to get him/her involved in troubleshooting the boards, since they know how it's supposed to work.

If you are asking the forum how to troubleshoot the issues, then you need to provide us with a lot more information (particularly, a schematic and an initial description of the multiple pulsing waveforms).