Doing something wrong? Testing low power inverters with Oscilloscope

[Destination: Moon]

Hi,

Was interested in seeing how good or bad inverters are. I'm new to solar and oscilloscopes..... Although I've always wanted one. Even though I don't know what to use it for.....

Attached are a few pics of my test results. All plots were auto ranged with me stabilizing the display. Some don't look right but I couldn't get them to look like I thought they should. Welcome any help or comments - thanks

 

[brb58]

Although I am not surprised at some of the inverter outputs, I am very surprised at what your 120V looks like. That must be a pretty cheap scope or you were not using a ground.

With 120VAC, you should be getting around 340V peak to peak. I am guessing you are using a 10X probe.

 

[Don B. Cilly]

None of them look right.
Did you take them under load? How big?

This is what the wave looks like on a 40-year-old Philips scope.
CCC (Cheap Chinese Clone - MUST pv1800 vmpk). Almost no load (<100W).

 

[Destination: Moon]

Although I am not surprised at some of the inverter outputs, I am very surprised at what your 120V looks like. That must be a pretty cheap scope or you were not using a ground.

I was using the ground. But your right, it's a tiny battery powered scope that I thought would be ok for hobby use but maybe not... Or I got a bad one. The plot of the household does look bad. Could the fact that it was from a coiled 50 foot extension cord be creating distortion?

 

[Destination: Moon]

None of them look right.
Did you take them under load? How big?

This is what the wave looks like on a 40-year-old Philips scope.
CCC (Cheap Chinese Clone - MUST pv1800 vmpk). Almost no load (<100W).

View attachment 93355

Yes, I was powering 2 incandescent light bulbs with the inverters at the time. Figured that would show the power quality?

But thinking some more, the scope has a signal generator and the sine wave looked really good, at 1khz and low voltage

 

[brb58]

I was using the ground. But your right, it's a tiny battery powered scope that I thought would be ok for hobby use but maybe not... Or I got a bad one. The plot of the household does look bad. Could the fact that it was from a coiled 50 foot extension cord be creating distortion?

That won't matter.

 

[Don B. Cilly]

I was powering 2 incandescent light bulbs with the inverters at the time.

5W each? 500W each?
What do they look like with no load?
-

 

[brb58]

I bought one of these a couple years ago on Amazon for $330 for hobby use...Arduino and stuff like that.

Rigol DS1054Z Digital Oscilloscopes - Bandwidth: 50 MHz, Channels: 4 Serial Decode Included: Amazon.com: Industrial & Scientific

Rigol DS1054Z Digital Oscilloscopes - Bandwidth: 50 MHz, Channels: 4 Serial Decode Included: Amazon.com: Industrial & Scientific

smile.amazon.com

More money now but it is a great scope for the money. I am a retired EE and am used to using scopes costing many times this and it holds it's own for home stuff. Originally I was going to buy a used Tektronix scope but this is WAY better.

 

[Destination: Moon]

5W each? 500W each?
What do they look like with no load?
-

The household was no load but from a coiled extension cord. The inverters were powering 135 watts. I disconnected one bulb and didn't see a change while I was testing. I'm probably gonna buy a better desktop scope. I'm fascinated by these things and they aren't crazy expensive nowadays

 

[RonP]

 

[efficientPV]

I've seen line AC look that bad though generally around industrial areas. The spikes at the peaks are where the H bridge flips, an extra long delay.