Kountryguy
Emery,SD
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Joined: 03/24/2002
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I have a Cobra Highgear 500 watt continuous, inverter. DC input voltage is 13.5. AC output voltage is 95.6. Any ideas what the problem could be? Might this be fixable, or should I just buy a new one? Thanks, Gil
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2oldman
WA
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Joined: 04/15/2001
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Yes, the meter you're measuring it with doesn't play well with MSW. Just plug a lamp or something into it and see if it works.
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smkettner
Southern California
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Joined: 03/21/2005
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Get a true RMS meter to measure MSW inverter voltage. It is probably fine.
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tvman44
Southwest Louisiana
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As previously mentioned some chep meters do not work well with anything but a sine wave.
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2oldman
WA
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smkettner wrote:Get a true RMS meter Which may cost more than the inverter? 
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Kountryguy
Emery,SD
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What caused me to check the voltage was that the TV worked, but the Satelite receivers broke up on some stations. I wondered if voltage was the problem. Maybe not. The receivers works fine on shore power. Gil
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smkettner
Southern California
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MSW is probably the culprit for the signal issue.
Smallish sine wave inverters. $117 to $257
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2oldman
WA
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Voltage is not the problem. MSW is.
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Caseydon
Simonton, Texas
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2oldman wrote:smkettner wrote:Get a true RMS meter Which may cost more than the inverter?
Depends on how much the inverter cost -- and how much the TV's are worth.
This one's no Fluke, but it will work -- $90.
Casey
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wa8yxm
Wherever I happen to park
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Joined: 07/04/2006
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MSW inverter and peak reading voltmeter.
There are two types of voltmeters, one is a peak reading and the other is called a "True RMS" voltmeter. Not to get too technical but it is easier to make a Peak reading meter than a true RMS
RMS (Literally "Root, Mean, Square) represents the area between the power output"Trace"and the base line.
Peak, represents the maximum (And minimum) vale of the trace.
The difference, is that becuse of the "Stair step" shape of the MSW wave form it peaks at a lower voltage I believe a peak reading meter, looking at 120 volts RMS, actually sees sometihng like 84.84 volts peak (or 169.68 volts peak to peak) It then multiples by 1/sqrt(2) to get the RMS voltage because for a TRUE sine wave, This is the conversion factor
but with the sharp rise and flat top of the MSW the Peak voltage does not go that high, so your peak reading meter, not knowing any factor other than 1/sqrt(2) gives a false low reading.
Nothin adds excitment like something that is none of your business
John is Near Kenwood TS-2000 housed in a 2005 Damon Intruder 377
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