Author Topic: Viewing Generator Output With an Oscilloscope  (Read 1716 times)

0 Members and 1 Guest are viewing this topic.

Offline tvlTopic starter

  • Newbie
  • Posts: 6
  • Country: us
Viewing Generator Output With an Oscilloscope
« on: January 02, 2019, 03:40:18 am »
Remove
« Last Edit: March 10, 2019, 12:19:56 am by tvl »
 

Offline basinstreetdesign

  • Frequent Contributor
  • **
  • Posts: 466
  • Country: ca
Re: Viewing Generator Output With an Oscilloscope
« Reply #1 on: January 02, 2019, 04:37:28 am »
I have used low voltage (120Vac - 6.3Vac) power step down transformers as audio output transformers in small amplifiers.  Testing them has taught me that they make pretty good wide BW transformers.  They will respond from below 50 Hz to beyond 40 KHz and are pretty linear.  As long as you do not saturate the core of the transformer then the output should show a pretty good rendition of the waveshape of the 120V source.  And the isolation provided, alone, makes it worth trying.
STAND BACK!  I'm going to try SCIENCE!
 

Offline David Hess

  • Super Contributor
  • ***
  • Posts: 17427
  • Country: us
  • DavidH
Re: Viewing Generator Output With an Oscilloscope
« Reply #2 on: January 02, 2019, 11:09:19 am »
My question is as follows: Whether the generator output be a PURE & CLEAN sinewave OR be DISTORTED & DIRTY, will the use of a step down transformer still provide me a true "picture" of the generator output quality OR will the transformer mask or make things appear differently …………… whether it be for the better or for the worse?

The sine wave is not very distorted but has residual high frequency noise from the inverter function.  Monitoring it through a small power transformer will work fine.
 

Offline soldar

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: Viewing Generator Output With an Oscilloscope
« Reply #3 on: January 02, 2019, 03:37:20 pm »
IMHO, if what you want to see is the actual waveshape then I would avoid a transformer because by introducing it you are introducing all sorts of unknowns. I think there is a much easier way.

Your scope has one of the leads grounded to earth (or you can ground it). Right?

You generator has one side of the output grounded (or you can ground it) . Right?

So you already have a common reference. Now you have 120 V rms on the generator's live wire and you do not want to stick the scope probe in there directly. Well, you can use two resistors to make a voltage divider and bring it down to a lower voltage.

My 'scope has a x10 (1:10) dividing probe.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 20357
  • Country: gb
  • 0999
Re: Viewing Generator Output With an Oscilloscope
« Reply #4 on: January 02, 2019, 04:21:30 pm »
IMHO, if what you want to see is the actual waveshape then I would avoid a transformer because by introducing it you are introducing all sorts of unknowns. I think there is a much easier way.

Your scope has one of the leads grounded to earth (or you can ground it). Right?

You generator has one side of the output grounded (or you can ground it) . Right?

So you already have a common reference. Now you have 120 V rms on the generator's live wire and you do not want to stick the scope probe in there directly. Well, you can use two resistors to make a voltage divider and bring it down to a lower voltage.

My 'scope has a x10 (1:10) dividing probe.
Only connect the x10 probe to the live wire. Don't connect the oscilloscope's chassis to the neutral or there's a risk a large current could flow through it, as the neutral voltage will be a bit higher than the earth voltage.
 

Offline rstofer

  • Super Contributor
  • ***
  • Posts: 9963
  • Country: us
Re: Viewing Generator Output With an Oscilloscope
« Reply #5 on: January 02, 2019, 04:30:06 pm »
Don't overlook loading the generator.  I would expect the waveform to change as a function of load.  I could be wrong (probably am).

If I were doing this, and I'm not, I would ask myself what I was going to do about it if the waveform is trash.  I probably wouldn't be thinking in terms of fixing it with a power conditioner so why bother to scope it?
 

Offline soldar

  • Super Contributor
  • ***
  • Posts: 3595
  • Country: es
Re: Viewing Generator Output With an Oscilloscope
« Reply #6 on: January 02, 2019, 06:36:48 pm »
Only connect the x10 probe to the live wire. Don't connect the oscilloscope's chassis to the neutral or there's a risk a large current could flow through it, as the neutral voltage will be a bit higher than the earth voltage.
Every generator I have seen has either the output totally floating or one side grounded. And same thing with the scope probes so I can't see any problem.

In any case, connecting only the probe of the scope without connecting the grnd reference is useless and will not give any useful info. The scope shows voltage differential between two points so you need to connect to two points.
All my posts are made with 100% recycled electrons and bare traces of grey matter.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf