Oscilloscope EXT. INPUT , source Channel#2

[danny davis]

the sweep will be triggered 60 times per second and if 400 Hz is selected, the sweep will be triggered 400 times per second.

Yes the horizontal linear sweep oscillator circuit will be triggered 60 times or 400hz times depends on the sync frequency right?

any other external trigger source.

What can you use a external trigger sources?

What would you call sourcing? or sources? you can source a O-scope channel to the triggers input

Trial and error. I would try various sweep rates and various sync sources until something made sense.

What various sync sources would you try and use?

By looking at a waveform, how do you know what the sync signals frequency is? how can you find out? where in the schematic would that information tell you?

when circuits I have tested have frequencys from 20hz to 20K hz that have a sync source of 60hz that display Stable not free running. The waveforms don't have to be multiples of the sync frequency

Why can't a sync source of 400hz has waveforms that range from 20hz to 20K? you're saying the waveforms have to be multiples of the sync source frequency in order to display them as STABLE not free running

Instead of any EXT sync selection, I would select Internal so as to use the waveform I am displaying as its own sync source. Then I would try various sweep rates until I could see one cycle of the signal displayed. Then I could estimate the frequency from the measured period on that display.

1.) That is only if the waveform signal and the sync signal are the same frequency? or a multiple of the sync signals frequency?
2.) Also that is only if the waveform signal so connect to ground and not floating, you're able to use the waveform that is displaying as it's own sync source. If the waveform is floating , how can you display it's own sync source?

Not necessarily. If it is truly floating, then it can be tied to ground without any problems. And then you can connect it to the scope. There are also battery operated scopes that are very well suited to scoping floating circuits, because the scope floats with the circuit.

You can also use a two channel O-scope as a differential setup, Channel#1 goes to HOT and channel#2 goes to COLD (-) , don't use the probes grounds , this is how to do floating measurements on an O-scope

If that other wire was actually 200 volts above ground, then your scope (if it is not a grounded scope) will now have its chassis ground elevated to 200 volts above ground, so that if you touch it, and some part of you is grounded, you will be electrocuted.

True , best to use an isolation transformer to plug your o-scope into for safety

 

[Tunelabguy]

True , best to use an isolation transformer to plug your o-scope into for safety

That does not mean you will be safe. If the scope is powered through an isolation transformer, the chassis of the scope can acquire whatever voltage is on the circuit you connect to the ground of the probes. Then if you touch the scope's chassis while some part of you is grounded, the current will flow through your body.

 

[danny davis]

That does not mean you will be safe. If the scope is powered through an isolation transformer, the chassis of the scope can acquire whatever voltage is on the circuit you connect to the ground of the probes. Then if you touch the scope's chassis while some part of you is grounded, the current will flow through your body.

So how do you be safe about this?

 

[BradtheRad]

What can you use a external trigger sources?

One time I used my scope to see if any spark plugs were misfiring in the car. (Since it runs on tubes I figured it would not be damaged from being near high voltage.)

I was not sure whether I would need to trigger it from cylinder #1.

What I ended up doing was to hook the probe to the center wire going to the distributor. (In fact there was no direct contact. I clipped the lead to a wire which I wrapped loosely around the spark plug wire.)

I set the sweep on free run, then fine-adjusted the sweep speed, so that 6 spikes appeared onscreen. (The engine had 6 cylinders.) This worked for my casual observation.

However suppose I had found it necessary to match each signal to its cylinder. Then I would need to trigger the sweep externally, from cylinder #1. I would need to hook up a second scope lead, to a wire around #1 spark plug wire.

 

[danny davis]

However suppose I had found it necessary to match each signal to its cylinder. Then I would need to trigger the sweep externally, from cylinder #1. I would need to hook up a second scope lead, to a wire around #1 spark plug wire.

That's a good example thanks