Is it pure sine wave?

[Mickel]

I bought a 1000W pure sine wave inverter off ebay for $230. So far it
appears to work quite well. From what I can test with a multimeter it
appears to be true to the figures quoted (standby currrent 0.6 amps, low
voltage alarm at 11V). But without a scope, is there a way to check if
it is really a pure sine wave unit?

Cheers,
Michael

 

[Phil Allison]

"Mickel"

I bought a 1000W pure sine wave inverter off ebay for $230. So far it
appears to work quite well. From what I can test with a multimeter it
appears to be true to the figures quoted (standby currrent 0.6 amps, low
voltage alarm at 11V). But without a scope, is there a way to check if it
is really a pure sine wave unit?

** Get an *AC* plug pack that can deliver say 6 volts at 1 amp and plug it
into the inverter.

Connect the 6 volt output to a decent hi-fi speaker and listen to the
sound.

A pure sine wave should be very deep and clean sounding.



...... Phil

 

[Trevor Wilson]

I bought a 1000W pure sine wave inverter off ebay for $230. So far it
appears to work quite well. From what I can test with a multimeter it
appears to be true to the figures quoted (standby currrent 0.6 amps, low
voltage alarm at 11V). But without a scope, is there a way to check if it
is really a pure sine wave unit?

**The term "pure sine wave" is a very rubbery one. The standard 240 Volt
mains supply can be termed pure sine wave, since it has respectably low
levels of distortion. To get any better than that, you will need to invest a
couple of grand into a mains 'reconstructing' device. PS Audio and others
make such devices. At HUGE cost. 230 Bucks is unlikely to buy you a device
with less than around 10% THD.

 

[Adrian Jansen]

I bought a 1000W pure sine wave inverter off ebay for $230. So far it
appears to work quite well. From what I can test with a multimeter it
appears to be true to the figures quoted (standby currrent 0.6 amps, low
voltage alarm at 11V). But without a scope, is there a way to check if
it is really a pure sine wave unit?

Cheers,
Michael

Ask yourself why you need 'pure' sinewave. If the inverter is to be
used for general purpose power for things like motors, lights, maybe a
PC power supply source, it does not matter at all.

If you power some critical piece of equipment that relies on low
harmonics in the supply line, like some transformer coupled low noise
power supply, then it may not work very well.

 

[Sylvia Else]

Ask yourself why you need 'pure' sinewave. If the inverter is to be used
for general purpose power for things like motors, lights, maybe a PC
power supply source, it does not matter at all.

I plugged an electric fan into a "modified sinewave" inverter, and not
only did the motor produce a buzzing noise, but it was clear from the
smell that the motor was overheating.

Sylvia.

 

[terryc]

I plugged an electric fan into a "modified sinewave" inverter, and not
only did the motor produce a buzzing noise, but it was clear from the
smell that the motor was overheating.

To be expected. You used a "modified sinewave" inverter. the rec was for
a "pure sinewave" inverter.

The approximate types are stages are
a) crap wave, looks all most like squarewave
b) "modified sinewave" has less steps than you have fingers and is over
priced crap,

c) "unspecified", has far more steps than fingers.
d) pure sinewave, aka should be smooth sine wave output.

 

[Sylvia Else]

To be expected. You used a "modified sinewave" inverter. the rec was for
a "pure sinewave" inverter.

The approximate types are stages are
a) crap wave, looks all most like squarewave
b) "modified sinewave" has less steps than you have fingers and is over
priced crap,

c) "unspecified", has far more steps than fingers.
d) pure sinewave, aka should be smooth sine wave output.

Yes. I read Adrian's comment as indicating that it doesn't matter what
form the wave takes for things like motors, etc., and that any inverter
would do. My experience shows that that's certainly not the case for motors.

Maybe his intent was that it doesn't matter if the wave diverges a bit
from a sinewave for the cases he identified. That's probably true.

Equipment that can't tolerate a moderate degree of harmonic distortion
is likely to be more trouble that it's worth.

Sylvia.

 

[Mr.T]

The approximate types are stages are
a) crap wave, looks all most like squarewave

In fact usually IS a simple square wave.

b) "modified sinewave" has less steps than you have fingers and is over
priced crap,

I real misnomer, what should be called a "modified square wave"!
Is usually one positive and one negative step with an off period in between
so that both the peak voltage as well as avearge voltage are now similar to
those of a sine wave. Waveshape remains roughly square.

c) "unspecified", has far more steps than fingers.

Unspecified can obviously be *anything* but most likely same as a)

d) pure sinewave, aka should be smooth sine wave output.

Should be a LOT closer than a) or b). Simply check the full load THD specs
if it's actually critical.

MrT.

 

[terryc]

Unspecified can obviously be *anything* but most likely same as a)

Not in my experience. YMMV.