Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Oscilloscope EXT. INPUT , source Channel#2

Status
Not open for further replies.
Billy, you really need to get a handle on Oscilloscope Basics. The Oscilloscope is a tool and unless you sit down and learn how to use that tool and what the tool is capable of you will never benefit from its use. Nobody here using an online forum can teach you how to use a scope, not completely anyway. Triggering on a scope is just one of many features with sub features, Internal, External, Coupling, Slope and Source with the list going on and on.

As to measuring the phase shift or phase difference between two signals? Since you mention 400 Hz we can look at 400 Hz. You have two 400 Hz signals so you can for example connect one 400 Hz signal to the CH 1 vertical input and the other to the CH2 vertical input. If CH 1 is your reference signal then set the scope to trigger off the CH 1 vertical input and set up channel 1 for a nice stable display. Let's see, by my math the time for a 400 Hz sine wave is 2.5 mS (0.0025 Second) so a sweep time setting of 1 mS / Div should be convenient and show a few repetitions of the signal, actually about 4 repetitions. If you use .5 mS / Div with 10 horizontal divisions the full sweep would be 5 mS and display two repetitions of your 400 Hz sine wave.

With triggering set for Channel 1 obtain a stable display. Set both vertical input couplings to GND and adjust the vertical positioning so both traces (CH 1 & CH 2) overlap. Next you return the vertical input coupling to AC. Using the vertical gain adjustments adjust the gain so both traces of your 400 Hz. are the same amplitude. You now have two 400 Hz. signals of the same amplitude overlapped on the screen. They should be stable with good triggering. Matters not where on the channel one signal triggering is happening. Hell if it makes you feel better then set the triggering for internal, CH 1, + Slope and adjust the level so the signal triggers on the + Slope right at zero crossover. It doesn't matter!

Now we know the time for one repetition of 400 Hz. is 2.5 mS. We also know that one repetition of our signal is 360 Degrees. Therefore 2.5 mS / 360 = .0000069 S or each degree = 6.9 uS of horizontal time.

OK, so look at a point on Channel 1 where one of the 400 Hz waveforms crosses the vertical center line. Work across to where the Channel 2 signal crosses the vertical center line. Measure the time between the leading edge CH1 point and the leading edge CH 2 point. Then divide that number by 6.9 uS. Lets say that CH1 leads CH2 by 69 uS. then you get 69 / 6.9 = 10 Degrees. So using channel 1 as the reference we can say channel 1 leads channel 2 by 10 degrees.

Don't want to use time? Cool and no problem. Count the minor divisions horizontally for one repetition of CH1 signal. You know 400 Hz. is 2.5 mS so if the time base is set for .5 mS / Div one repetition of 400 Hz should be 4 divisions and at 5 minor divisions horizontally per division that would be 20 minor divisions. OK so now 20 minor divisions equal 360 degrees so 360 / 20 = 18 degrees per minor division.

Now just as before measure from a point on the channel 1 signal (again a zero cross over is convenient) to the same point on the channel 2 waveform. How many minor divisions? Multiply the number of minor divisions by 18.

Ron
 
in the video section on here is a scope video for beginners its fairly long but packed full of information, might well be worth a look!
 
Thanks for the information Reloadron

What have you done in the past or in general when using the EXT input?

I want to know how to use the EXT input

Please give some examples would help me out
 
Here is somewhat of an illustration of what I was describing in my last post. You may want to check out what ghostman11 mentions.

There are times when using external triggering comes in handy. One example that comes to mind, that I used was running a 10 MHz standard signal (Frequency Standard) from a GPS receiver into EXT. TRIG. Then on CH1 display the standard frequency out of a frequency counter. Set the time base of the scope to something fast like .1 uS / Div. This allows one to observe the drift between a NIST traceable standard 10 MHz signal and the internal oscillator frequency of a lab standard frequency counter. Billy, there are hundreds of reasons to use external triggering. I simply do not see why you need it for what you are trying to do with phase.

Phase Shift.png
 
Because I'm trying to learn how to use the EXT input jack on the O-scope

I have never used it or what it is used for, examples would help me out a lot

Can you just give some basic examples on how to use the EXT input jack , it would help me out a lot
 
i have hooked the ext trigger to the LA so i can see if there is a glitch. My advice would be too look at that video and then look at the guys you tube vid, he worked for textronix as an engineer and has a good style of teaching.
Asking others for examples of how they have used it isnt going to teach you how or when to use it, for that you are going to have to learn some stuff, the best way for this kind of thing is decent you tube video's so you can see the waveforms. Also on most video's that are good the people that make them answer any questions you may have in the comments part.
NO SHORT CUTS to learning sorry
regards
Jason
 
I have no idea what you have available to play around with. However, if you just want to get acquainted with using external triggering there are some things I guess you could do.

If you have a function or waveform generator some have a sync out or trigger out. Run a signal into the vertical input of the scope. Run the sync or trig out to the scopes external trigger in. You won't see anything that you wouldn't see using internal triggering but you will be using external triggering. Scopes like most test and measurement equipment have features. External triggering is just that, it is a feature. The more you become familiar with the scope the more you know how and when to use the features. Different scopes by different manufactures have different features and capabilities. You as the end user of the scope determine when to use what features for what. This goes full circle back to getting to know your scope, what it can and can not do and why.

Ron
 
NO SHORT CUTS to learning sorry.

So that explains it huh? Really glad that my dad explained that to me some 50 years ago as I would have spent considerable time looking for those elusive short cuts. When I would ask my father redundant questions looking for a short cut or easy way he would look at me and hand me a book. Next time I would ask he would ask if I actually read the book. :)

Damn, I miss that guy.
Ron
 
and my father is where i learnt it, like you i too miss him, i am also trying to teach LG the same thing, once you older you suddenly realize that all shorts are infact just the quickest route to the long way round ;), asking questions is a good thing if the question is a good question. However it is easy to spot the questions that are designed to save someone the trouble of learning what they need to know.
 
People are starting to get too snippy around here again.
I had an old single trace scope and pickups from an automotive scope. I used the main pickup on the coil wire to the scope input. The external trigger went to #1 spark plug wire. That way I could see all 8 cylinders, starting with #1.
Now I have a cheap Pintek dual trace scope. It has a 4 position switch for trigger input. CHA, CHB Line and EXT. Does yours have Line trigger input and would it serve your purpose?
 
Last edited:
Tektronix 2445 A , Tektronix 2445B

I use another one , I will get the name tomorrow that has the EXT. Trigger

Those are nice scopes. Remember how I mentioned 'features", they offer up some nice handy features. Remember th discussion about phase? I glanced at the operator's manual and there is a good write-up about phase measurements using the cursor feature, cursors and on screen display are a few real nice features. Makes it real easy to scroll with the cursors to the zero crossover points I had in the cartoon image I posted, plus the scope readout will display degrees. Pretty sweet. Most manuals, especially Tektronix manuals give some good examples of how to do various measurements.

Ron
 
Does yours have Line trigger input and would it serve your purpose?

It does, But I'm measuring an AC waveform at 115VAC at 400hz, that's why I need it as an EXT INPUT

My question is that can I inject a 115 VAC voltage into EXT input or Channel#1 without damaging the O-scope , or do I need to use an AC Ratio Step down transformer to step down the 115VAC down to 26VAC or something to make it safe so it doesn't damage the O-scope
 
The Unit or circuit board I'm testing doesn't plug into the wall 120VAC at 60hz, it uses 115VAC at 400hz to be powered , the power supply won't work with 120VAC at 60hz only at 115VAC at 400hz , that's why the O-scope is displaying free running waveforms

That's why I need the oscilloscope to SYNC up to a 115VAC at 400hz not at 120VAC at 60hz

I'm not measuring a phase angle , it's about SYNC the O-scope up to a different AC LINE

What is this called that I'm am doing? it's about Syncing not measuring phase angles of two different waveforms
 
surely it triggers from the wave form? not the mains, if you probe the psu with one channel and the pcb with the other then i dont see what the line voltage has to do with it
 
Tektronix 2212, 2445, 2235, 2215

can i put 115vac 400hz mains line on the ext input without damage?

I could look it up for you, but it's time you learned how to find something out for yourself.

Find a manual or spec sheet for the scopes, and see what the limits are for that input.
 
Tektronix 2212, 2445, 2235, 2215

can i put 115vac 400hz mains line on the ext input without damage?

Most Tektronix scopes have the max input allowed noted right beside the connector. My scopes all show 400 V Pk. Just remember what I mentioned earlier. These scopes do not have isolated differential input channels. The outer shields on all of the In/Out connectors are common. Read the manual! The manual for the specific scope you plan to use.

Ron
 
If a circuit is triggered by an event, input voltage or current, my manager said I have to use a storage o-scope because the circuit is triggered by an event is this true cant use a non- storage scope?
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top