Testing for sine
I have a military, trailer mounted, 4-cyl. diesel generator made in the mid '50's.
Use it all the time - I'm off-power. You set the engine speed to the desired cycles and then dial in however many volts you want.

I would like to know if it puts out true/pure sine but don't know how to determine that. Any advise, tips, information appreciated.

 

You need to look at the wave form with an Oscilloscope to see its purity.

http://www.google.co.uk/imgres?imgu...nJ8LKhAeco4CoAQ&sqi=2&ved=0CE8Q9QEwBA&dur=336

 

Most AC power generators put out a fairly good sine-wave. If you need to measure it then an Oscilloscope is the best way, as suggested by Dd.

 

Thanks for that; and the confirmation. I'll check out "Oscilloscopes for dummies".
Re: "Most AC power generators put out a fairly good sine-wave." Would that apply to one made in the 50's?

 

Probably, it's natural for an AC generator to make a sine like waveform as it is a rotating device and sinewaves are a math form that comes from a circle.

If your AC generator has fixed RPM and you "dial in the voltage" it probably is an AC generator with adustable field. It will probably be sine-like unless overloaded.

Maybe you should say why you need a good sine shaped AC? There might be specific issues.

 

It doesn't have a fixed RPM. The engine speed is adjustable for the purpose of setting the cycles per second on the meter [range 50 to 65]. I rarely have to adjust the engine speed once the cycles are set at 60. [For some reason on the door it says to set it at 61.8 cycles at initial start up - I never do. This is a heavy duty US Army tactical unit I purchased 25+ years ago at a DOD auction].
With the cycles set, you can dial in whatever voltage you want. I usually dial in 112 to 116 volts due to the length of extensions I'm using. I use to set it at 125 volts thinking of the possible loss of voltage in the lines but destroyed a vacuum motor.
As to need for true sine, there are no utilities in my area and I use a lot of battery stuff: tools, laptop, cell phone and don't want to damage the batteries - so I never charge them with this generator [go into town for that]. Be nice to charge them when I need to use electric power tools or hair dryer to defrost the gas fridge.

 

Generators are normally designed to put out a good sinewave since any harmonics tends to reduce efficiency and increase heating in the generator. If it was designed for the Army, it likely was built very well and I would expect the output to be a good sinewave.

Generally the only devices that output a sinewave with significant distortion are electronic inverters since it requires a more elaborate and expensive circuit to generate a low distortion sinewave with those devices.