Hello,

You might want to have a look at the "XYZ of scilloscopes" book:
http://whites.sdsmt.edu/classes/ee320/labs/XYZs_of_Scopes.pdf

Bertus

 

So the Auto trigger mode needs a Longer wait time for low frequencys? but why does it need a longer wait time?

It doesn't make sense to me as to why

Really?
Ok look at it this way, your signal say is every hour, and your trigger every 15 mins.
So the trigger waits for 15 mins for a signal to come along that is above the trigger set point, well if your signal is only once an hour then after 15 mins the trigger say's " oh well nothing here so I will trigger and wait again"
I used exaggerated times for you to get the point. If you put it in normal mode, then the trigger just sits there all day smoking a fag and drinking beer waiting for a level above it threshold, unfortunately for Mr Trigger every hour a threshold in this example comes along, so Mr Trigger puts down his beer once an hour and does his thing.

Does that make sense? Obviously replace mins and hours with appropriate times, and no the trigger in reality the trigger only smokes if something has gone very wrong, (no idea if it drinks beer)

Your very best friend on the internet
LG

 

Really?
Ok look at it this way, your signal say is every hour, and your trigger every 15 mins.
So the trigger waits for 15 mins for a signal to come along that is above the trigger set point, well if your signal is only once an hour then after 15 mins the trigger say's " oh well nothing here so I will trigger and wait again"
I used exaggerated times for you to get the point. If you put it in normal mode, then the trigger just sits there all day smoking a fag and drinking beer waiting for a level above it threshold, unfortunately for Mr Trigger every hour a threshold in this example comes along, so Mr Trigger puts down his beer once an hour and does his thing.

Does that make sense? Obviously replace mins and hours with appropriate times, and no the trigger in reality the trigger only smokes if something has gone very wrong, (no idea if it drinks beer)

Your very best friend on the internet
LG

LG has explained this quite clearly, above.

Different scopes will implement they Auto trigger timer differently, so it's impossible to tell you where in the schematic of YOUR scope this is done, or how it's done.

I'd also recommend reading the XYZs of Oscilloscopes as recommended by Bertus.

The answer to all of your questions have been presented here, in a number of different ways.

 

Auto trigger timer differently

oh ok so it's a timer circuit

I didn't know it was a timer circuit

So what you're saying is that if the timer circuit is timed short it will turn on or off before it can detect a trigger threshold from a low frequency

A Timer circuit that has a short time is for high frequencys
A timer circuit that has a long time is for low frequencys
If the Timer circuit was longer it will turn on or off to dectect a trigger threshold from a low frequency waveform

 

oh ok so it's a timer circuit

I didn't know it was a timer circuit

So what you're saying is that if the timer circuit is timed short it will turn on or off before it can detect a trigger threshold from a low frequency

A Timer circuit that has a short time is for high frequencys
A timer circuit that has a long time is for low frequencys
If the Timer circuit was longer it will turn on or off to dectect a trigger threshold from a low frequency waveform

NO. What we are saying is, sometimes you have to put the trigger in normal mode and sometimes you dont, sometimes you have to use single shot and sometimes you dont, sometimes you have to use rising edge and sometimes you dont, sometimes you have to use repetitive mode and sometimes not, sometimes you have to use a smart trigger and sometimes not, sometimes you have to use external trigger and sometimes not.
IN FACT the only thing you always have to do is

RTFM
And get to know the equipment your using! It matters not what goes on regarding trigger timer, if you cant capture it on auto you try normal or another setting. Why are you obsessed with making equipment work the way you want, rather than work with how the equipment does something?
Unless your designing a oscilloscope just use what works! It isnt a big deal you just push a button

 

Just to say this. It will be almost(if not) impossible to catch a RS232 single byte+start/stop bits on a analog scope. Even on a digital scope it may require some test and trail. And if several bytes are sent. It will be more or less random what part of the transmission you can get. For analyzing a unknown RS232 or other similar serial datastream. A logic analyzer is the correct tool. A scope without a logic analyzer function is not and will never be the correct tool

 

Why use a logic analyzer , does it have a different triggering circuit built in VS a O scope?

A Logic Analyzer is better for what kinds of measurements VS an o-scope?

 

A Logic Analyzer is better for what kinds of measurements VS an o-scope?

Hm, have you tried turning the brain off and on again? A logic analyzer is used to look at logic level signals, aka digital signals. Oscilloscope is used mainly for analog signals, even though you can try looking ata digital streams it will rarely make any sense on an oscilloscope.
If you have a digital scope with deep enough memory then it should be possible to catch what t06afre was talking about, but you will be out of luck with analog scope.

 

Why use a logic analyzer , does it have a different triggering circuit built in VS a O scope?

A Logic Analyzer is better for what kinds of measurements VS an o-scope?

For digital signals you cant beat a Logic Analyzer or its trigger ability, I have several HP ones the best of which has a complex trigger system that can be set up to trigger on almost any and every condition, or combinations of conditions, it also has a built in oscilloscope which is handy to capture glitches etc.
BUT an oscilloscope and Logic analyzer are completely different tools! Yes on my DSO I can capture RS232 data without much hassle, but why would I? Instead I would use Logic analyzer for that.
I think part of the problem you have is not understanding what tool to use for what job.
The other problem to use an analogy is like this
say you was a car mechanic sorting out a fuel issue on car, for most they would hook up the equipment and take the readings and go from there, with you, its not enough. You get the answer on the fuel question then want to know how the test equipment found the answer! You and your questions are all over the place, there is no sensible form to them, you use phrases that you think will make you seem like a real engineer, but often they are out of context or totally baffling like the whole pulse train and frequency thing!
Go back and start again at the beginning, learn the basics like I am having to do, or your just going to keep getting lost
best regards
LG

 

Different scopes will differ in how long the AUTO trigger mode "waits" until it automatically sends the sweep. Try using the Normal trigger mode.

AUTO trigger does not automatically setup the trigger. It only sends a sweep automatically if a valid trigger event is detected in some time period (which varies between scope models).

IIRC, my scope has a setting for what is called onhold for when in trigger Auto mode.

IIRC again, the minimum (and default) is 100nsec. I should check that to be sure.

 

NO. What we are saying is, sometimes you have to put the trigger in normal mode and sometimes you dont, sometimes you have to use single shot and sometimes you dont, sometimes you have to use rising edge and sometimes you dont, sometimes you have to use repetitive mode and sometimes not, sometimes you have to use a smart trigger and sometimes not, sometimes you have to use external trigger and sometimes not.
IN FACT the only thing you always have to do is

RTFM
And get to know the equipment your using! It matters not what goes on regarding trigger timer, if you cant capture it on auto you try normal or another setting. Why are you obsessed with making equipment work the way you want, rather than work with how the equipment does something?
Unless your designing a oscilloscope just use what works! It isnt a big deal you just push a button

Haha, I had to look that up, but wasn't very surprised by that definition:

https://en.wikipedia.org/wiki/RTFM

"RTFM is an initialism for the expression "Read the ******* manual" (sometimes flaming or another metaphor or profanity) or, in the context of a Unix environment, "Read the ******* man page" (see man page)."