Measuring inverter output

[guy99]

I have a small (175) watt inverter that the PO used to run a small flat screen TV/DVD. I plug it in to my running Yukon and measure the output voltage with my cheapo Harbor Freight digital VOM set to the 200 V ACV scale. The reading I get is ~90. Does this mean the inverter is not putting out the correct voltage or is this an artifact of the the non sine wave output and/or the cheapo meter?

[TomW]

Is the television or other load hooked up when you measure this voltage?

Tom

[guy99]

Originally Posted by TomW

Is the television or other load hooked up when you measure this voltage?

Tom

Nope, I am sticking the probes from the meter into the 120V socket on the inverter. The inverter is plugged into a power point on my Yukon and the Yukon is running.

[TomW]

Don't worry about it then.

If the inverter is under any type of load and you measure anything under 110 vac, then you need to borrow a better meter to confirm the fact.

110 vac is generally accepted as the lowest "safe" voltage to run most devices (i.e. the load plugged in to your converter).

Tom

[guy99]

Originally Posted by TomW

Don't worry about it then.

If the inverter is under any type of load and you measure anything under 110 vac, then you need to borrow a better meter to confirm the fact.

110 vac is generally accepted as the lowest "safe" voltage to run most devices (i.e. the load plugged in to your converter).

Tom

So, the voltage should GO UP when I put a load on the inverter?

[TomW]

Originally Posted by guy99

So, the voltage should GO UP when I put a load on the inverter?

The inverter's output voltage is only valid when the inverter is under load.

So "yes".

Tom

[guy99]

Here are the results:

Inverter with no load reads 90V
Inverter with 75 Watt load reads 98V
Meter reads 116V from 120V socket in MH (connected to 30 amp source)
Meter reads 115V from a different inverter with the 75 Watt load
The other inverter has a display which shows what what it thinks the volatge is, it reads 115V.

So, it seems that the first inverter is not putting out the proper voltage?

[TomW]

Originally Posted by guy99

Here are the results: ... So, it seems that the first inverter is not putting out the proper voltage?

At face value I would agree. But with true RMS voltage & inverter technology what it is I will not offer a final opinion.

There is a rivet master who, in my early days on the forum, impressed me greatly with his insight into inverter applications. I PMed him on your behalf.

If we are all lucky, he will share the right answer.

Tom

[RoadKingMoe]

Looks like your meter is okay, and maybe the little inverter is weak. One thing worth checking is plugging it in somewhere else, like the actual cigarette lighter. The "power point" may not be wired as heavily and and could be dropping input voltage to the inverter. I'd also try it in another vehicle.