Viewing Waveform of an Inverter

Checking the waveform on a car plugin type Inverter, like the type you would use to power a laptop computer in a car.
I used my NLS MS-215 Miniscope to view the waveform.
As you can see it is much more like a square wave than a sine wave, more like a staircase waveform.
It is called a "modified Sine Wave" but look at the scope, it is a "stairCase" nothing even looking like a sine wave or so called "Modified" sine Wave.
The scope used in this video can't respond to the fast rise time of the waveform, put your small inverter on a real good scope and you will see a "staircase" waveform.
These will be fine for things like razors, light bulbs, even tv's as I have used it for that.
I would not want to use it to power a laptop computer, although it may be ok, but would you want to chance it??
Get yourself a DC to DC converter (12 to 19 V. depending on your computer) if you want to use your laptop in the car, they do sell thim.

Category:

Education

Tags:

• Education
• Oscilloscope
• Waveform
• Inverter
• Electronics

[quadmasta7]

i tried running an xbox 360 and it just shut off because it wasn't a pure sine wave inverter... o well ...

[old64goat]

@quadmasta7, Yes that what I tried to explain to some people that seem to say it is okay to use this on some solid state stuff.

These inverters do NOT put out a sine wave, it is a square wave, a modified square wave non the less.

You can call it a modified sine wave, but it is NOT.

It was a good thing your X-Box 360 shut down, the inverter could have ruined it.

[kenster2001]

I have audio glitches and general touch pad funkiness when I charge from an inverter. It doesn't seem to damage the laptop though.

You can charge the laptop from an inverter, but you might not want to operate it while its charging.

[old64goat]

Hi Kenster2001, Yes I agree charging a laptop should be okay but I would not use the laptop while it is plugged into an inverter.

[Amishman35]

A modified sine wave inverter is probably OK for equipment that uses switch-mode power supplies, but for something like a pre-1990s stereo system or an analog TV set, you'd probably have more noise in the signal you are viewing/listening to. And don't get the energy to power a scope/spectrum analyzer's AC plug off an inverter like this...you'd probably get inaccurate readings on the measurements.

[old64goat]

I agree Brent, I would only use them for lighting or a power drill.

Bill

[ForViewingOnly]

Interesting to see the modified sine wave, thanks for uploading. Was the inverter output on a load or open circuit? I wonder if the waveform would be smoother if a load was attached? That's a beautiful little CRT scope you have there - never seen such a small CRT before!

[pyrobryan]

It is similar to a square wave, but has the distinction as a modified sine wave because of the zero state between the crest and the trough, where a square wave has no zero state and cycles directly from crest to trough and back.

[an1m3n00b]

@old64goat It could have just been too low powered too, xboxes do use a fair amount of power

[smeezekitty]

I'd like to correct you here:

Computer power supplies for desktops and laptops are switchmode, meaning they rectify and well filter the input so it shouldn't make any difference.

Also, this is a 3 step wave, not a 2 step square wave which is much worse as it does not output the correct RMS voltage which could damage computer power supplies.