Oscilloscope EXT. INPUT , source Channel#2

[Billy Mayo]

Using a DUAL TRACE SCOPE, You would put One into channel-1 and the other into channal-2
This will allow you to see the Phases, Relative to each other.

No , I had to use channel#1 as the AC output which has a polarity switch to go from 0 to 180 degrees
Channel#2 I had to put 115vac 400hz and on the O-scope set it to SOURCE on channel 2

This allowed me to view the AC waveform at either 0 or 180 degrees

I used the Channel#2 as a SOURCE REFERENCE

Can't I put 115VAC on the EXT. INPUT on the O-scope and use this as a SOURCE REFERENCE ?

I'm just not sure if i can put an AC waveform input on the EXT INPUT on the O-scope and how much voltage can I put into it?

Why can't I put 115VAC at 400hz on the EXT INPUT on the O-scope? so that channel#1 and channel#2 can SOURCE to the ext input

 

[Billy Mayo]

What have you guys done in the past or in general when using Channel#2 to be the reference and having channel#1 Source to channel#2?

What have you guys done in the past or in general when using the EXT input? using reference waveforms or what kind of references

 

[Reloadron]

First of all I haven't a clue what scope you are using or its capabilities. I will tell you this. Most scopes share a common. If you try and run 115 VAC (Line Voltage) into the external trigger in and have line and neutral reversed things will get ugly real quickly.

What exactly are you trying to do? Exactly meaning define in detail.

I left you with this link in the other phase related thread. Did you try it?

Ron

 

[Billy Mayo]

If you try and run 115 VAC (Line Voltage) into the external trigger in and have line and neutral reversed things will get ugly real quickly.

So what can I put into the External trigger INPUT?

Can I put 115 VAC in the External trigger input? or will it get damaged?

I'm not sure if I can put an AC signal or voltage into the External Trigger Input

Are Channel#1 and Channel#2 , isolated grounds? or the tied together to ground?

 

[Billy Mayo]

I left you with this link in the other phase related thread. Did you try it?

No, I'm not trying to measure to different AC waveforms , and trying to measure the phase shift or time between them

 

[chemelec]

The Channel-1 and Channel-2 are on a "DUAL TRACE" SCOPE.
Channel-2 is NOT the Same as an EXT INPUT.

BILLY, You have a LOT TO LEARN

 

[Billy Mayo]

The Channel-1 and Channel-2 are on a "DUAL TRACE" SCOPE.
Channel-2 is NOT the Same as an EXT INPUT

.

Yes I know that

But you can use channel#2 as a reference and Source Channel#2 to channel#1

This is a form of Triggering right?

Why Can't you use the EXT INPUT like this?

 

[Reloadron]

The link shows how to measure phase shift. Thus the title of Oscilloscope Phase Shift Measurements.

I told you, nobody here knows what scope you are using. I have no idea if the in/out share the same common but most general purpose scopes do. Furthermore, most scopes allow for line triggering so if the 115 VAC you plan to inject into the external trigger jack is line voltage just use the line trigger function.

Ron

 

[Billy Mayo]

Can I inject 115VAC at 400hz into the External trigger jack?

I will get the model names tomorrow at work , I don't them off hand sorry

 

[Reloadron]

Read the manual for the scope. The scope manual will tell you the limitations for external trigger in.

Ron

 

[Billy Mayo]

The scope manual will tell you the limitations for external trigger in.

Ok, but what have you used this for ? bench check or tested a circuit in the past or in general

Give examples please so I can learn how to use the external trigger input

 

[ChrisP58]

The only times I have ever used the External trigger input on a scope was when I need to see the timing of two signals with respect to a third signal. And that was for square waves in a digital circuit, so I only needed to know where the edges were. One big problem that I see with trying to use the Ext input to measure phase of something like a sine wave, is that you can't actually see the waveform, which makes it difficult to know where to make your timing reference from.

Why do want to use the External input instead of the two regular channels?

 

[Billy Mayo]

Why do want to use the External input instead of the two regular channels?

1.) So I can have more channels to display inputs and outputs and not use up a channel
2.) I think using the External input would LOCK SYNC the reference 115VAC 400hz AC waveform with Channel#1

Using Channel#2 as the Reference at 115VAC 400hz AC waveform doesn't SYNC , so you don't know where the beginning of the waveform is on channel#1 , I have to use the trigger level to find a starting point

Doesn't the External Input SYNC up better when used as a reference?

trying to use the Ext input to measure phase of something like a sine wave, is that you can't actually see the waveform, which makes it difficult to know where to make your timing reference from.

This is the same problem I'm having when using Channel#2 as the reference source

 

[ChrisP58]

1.) So I can have more channels to display inputs and outputs and not use up a channel

You only need two channels to check the phase of two signals. Why do you need a third?

2.) I think using the External input would LOCK SYNC the reference 115VAC 400hz AC waveform with Channel#1

Yes, but at what threshold voltage?

Using Channel#2 as the Reference at 115VAC 400hz AC waveform doesn't SYNC , so you don't know where the beginning of the waveform is on channel#1 , I have to use the trigger level to find a starting point

If you want to sync to the signal on channel #2, you set the trigger source to Ch #2. And yes, you set the trigger level to whatever threshold you want to use as the a reference point. For an AC sinewave you would typically use zero volts to get the zero crossing point. Please note, for phase measurements, you trigger on only one channel. You then use your eyes and the cursor to find the same point on the waveform showing on the second channel.

Doesn't the External Input SYNC up better when used as a reference?

I can't imagine why. My experience is that the ext input has fewer trigger options.

This is the same problem I'm having when using Channel#2 as the reference source

Are you saying you can't see the waveform on the 2nd channel? If so, you have it setup wrong, or a broken scope.

 

[Billy Mayo]

Yes, but at what threshold voltage?

What Threshold voltage would an AC 115 VAC be? at what threshold hold voltage?

you set the trigger level to whatever threshold you want to use as the a reference point. For an AC sinewave you would typically use zero volts to get the zero crossing point.

Well how do you get the threshold hold to be at zero volts?

The AC waveform moves from left to right when you move the Trigger level - or +

trying to use the Ext input to measure phase of something like a sine wave, is that you can't actually see the waveform, which makes it difficult to know where to make your timing reference from.

Why does it make it difficult to make the timing reference using the EXT INPUT?

 

[ChrisP58]

What Threshold voltage would an AC 115 VAC be? at what threshold hold voltage?

I would choose zero volts, to set the zero time reference at the zero crossing point.

Well how do you get the threshold hold to be at zero volts?

My Tek TDS5034 has a display that shows what the trigger voltage is, so I set the level at 0.0V. I don't know about your scope.

The AC waveform moves from left to right when you move the Trigger level - or +

As it should. You are changing the voltage of the trigger point, so of course the waveform will change position.

Why does it make it difficult to make the timing reference using the EXT INPUT?

I don't know the details of your scope, so I really shouldn't speculate. But why don't you just make it easy on yourself and do it the simple way?[/quote]

 

[Billy Mayo]

I would choose zero volts, to set the zero time reference at the zero crossing point.

On channel#1 or on Channel#2? which channel do you do this for?

 

[ChrisP58]

On channel#1 or on Channel#2? which channel do you do this for?

It really does not matter. You can use either channel as the reference, since you are only looking for a time difference.

 

[Billy Mayo]

Yes i know

that shows what the trigger voltage is, so I set the level at 0.0V

for the reference channel do you set the Trigger level to Zero? or the other channel?

Why do you think the EXT. INPUT is limited and has limited triggering?

Why do you think using a Channel as a reference is better than using the EXT. INPUT?

Can you put in DC or AC waveforms into the EXT. INPUT?

 

[ChrisP58]

for the reference channel do you set the Trigger level to Zero? or the other channel?

Whichever channel you are using as a trigger source. Again, for measuring a time difference it doesn't matter which is which.

Why do you think the EXT. INPUT is limited and has limited triggering?

Why do you think using a Channel as a reference is better than using the EXT. INPUT?

Can you put in DC or AC waveforms into the EXT. INPUT?

Again, without knowing the details of YOUR scope, I can't say.