Inverters - Page 2 - Fiberglass RV


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Old 02-11-2003, 04:57 PM   #15
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Noel
Thanks.You got me working now.Running all over the place.;)
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Old 02-11-2003, 05:04 PM   #16
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Noel
I am running 2- 100 amp batteries.So this should put me in a range of 25 run hrs plus.:conf
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Old 02-12-2003, 12:37 AM   #17
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Hi Folks,:wave

Geek alert! Geek Alert! Just a couple (dozens?) of words regarding ''inverters'', ''modified'' sine waves, ''real'' sine waves, average responding meters and true rms meters.:zz

I saw these postings about low voltage out of a power inverter so I just had to do a little experiment.

I just happen to have a little 300W inverter sitting on my junk pile... errr uh I mean my instrument bench, just waiting for a purpose in life. A ha! I thought, I might just hook it up to a 12 volt battery and measure the no load output voltage.

With a 12 volt input that lousy thing only put out a measly 104.1 Vac. I thought to myself Costco sure screwed me when I bought that piece of junk! Uh but wait a minute, I seem to recall some of the fine print that mentioned something about "true RMS" responding meters........

Soooooo When I measured the no load output of that piece of junk with a true RMS meter it said 123.2 Vac. Much closer to the promised 120 Vac that the inverter advertisement barked about.

Beware of this idiosyncrasy! When measuring the ''modified'' sine wave voltage with an average responding meter the value you get is BOGUS! Most average responding meters measure the average ac voltage and scale it to an RMS (root mean square) value for a pure sine wave, just like you get out of your wall socket. This trick won't work with a square wave, or a triangle wave, or a rectangular wave, or a sawtooth wave or ANYTHING except a true sine wave. Each of these signals have a different scaling factor that relates the average value to the RMS value. The scale factor that equates the average of a sine wave signal to the RMS value of said signal is NOT the same factor that equates a modified sinwave signal to its RMS equivalent. Using an '' average responding'' meter to measure ANYTHING except a purely sinusoidal signal is kinda like trying to measure the dimension of a square hole with a round pin gauge.

The moral of the story is that to measure the actual heating power of juice from a modified sine wave inverter takes a good, and of course, more expensive True RMS meter.

End of Geek alert. Hopefully, this makes things less murky.
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Old 02-12-2003, 01:11 AM   #18
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OK:conf Its amazing how each person here can relate to different areas of disscussion and have a answere.:wave
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Old 02-12-2003, 07:42 AM   #19
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Quote:
Orginally posted by John Ballard
Beware of this idiosyncrasy! When measuring the ''modified'' sine wave voltage with an average responding meter the value you get is BOGUS! Most average responding meters measure the average ac voltage and scale it to an RMS (root mean square) value for a pure sine wave, just like you get out of your wall socket. This trick won't work with a square wave, or a triangle wave, or a rectangular wave, or a sawtooth wave or ANYTHING except a true sine wave. Each of these signals have a different scaling factor that relates the average value to the RMS value. The scale factor that equates the average of a sine wave signal to the RMS value of said signal is NOT the same factor that equates a modified sinwave signal to its RMS equivalent. Using an '' average responding'' meter to measure ANYTHING except a purely sinusoidal signal is kinda like trying to measure the dimension of a square hole with a round pin gauge.
Oh!! Man!!, John, does this make me a geek? I understood this paragraph. well I understood the others too, but I like this square hole - round gauge analagy. :lol
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Old 02-12-2003, 07:55 AM   #20
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Ms. Journeycake, I understood------

--------about the ''sinusoidal signal''.

That's a medical term meaning that a person is ''ready to sneeze.'' Right?

Now that I've passed pre-med, find me a course in pre-Electrical Engineering 101. :zz
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Old 02-12-2003, 08:02 AM   #21
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Gosh, George. maybe I really glosses over, a few words, but I got the concept. :o
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Old 02-12-2003, 04:46 PM   #22
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One thing you may find when trying to run a color TV with an inverter is that the startup for the color involves the degaussing circuit, so the draw in enuf to start to bog the inverter down -- If your inverter is attached to an outlet with typical wiring, the wiring loss will be enuf that the inverter shuts itself down for low input voltage. Either beef up the 12VDC wiring between the outlet and battery or get an direct-connect outlet that you clamp directly onto the battery and then carry the 120VAC back to the TV with a household extension cord (getting a bigger inverter will NOT solve this problem).

Actually, anytime you are using an inverter, you will get more efficiency by having the 12VDC run as short as possible and taking your distance-based voltage losses on the 120VAC wires.

Pete and Rats in the rain?!? in Death Valley
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Old 02-13-2003, 09:18 AM   #23
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We bought an 800 watt inverter for our truck to run a dorm fridge while on trips. Love that thing! Recently the power went out, to our ranch, and we were able to watch satellite tv on our 31 incher. Was a bit weird, to be watching tv with the Coleman lamp burning. We just ran a cord into the house from the truck, pointed the truck into the wind and plugged in. That inverter has a thousand uses. I never need those 12v adapters for anything, laptop, cell, shaver, halogen work light and my favorite, yet illegal, Christmas Lights on the truck. Seems only local sheriffs care, never been bothered by State Highway Patrols, so I only use 'em on the interstate around Christmas time. I get big grins and pointing finger from all types!
:o

Was bit of a trick to get the fattest wire the shortest distance from the battery to the cab.
:o
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Old 02-13-2003, 09:24 AM   #24
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?

:conf Think I'll buy me a longer extension cord.
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Old 04-01-2003, 07:15 PM   #25
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Hi All
I just thought I would move this thread up front.I finnally got my inverter hooked up and running.It runs the TV and VCR at same time.Also runs Satilite Dish.Iam Happy now.It gives me what I want.:wave
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Old 04-02-2003, 12:15 AM   #26
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Quote:
Orginally posted by Chester Taje

* * * * * * Hi All
I just thought I would move this thread up front.I finnally got my inverter hooked up and running.It runs the TV and VCR at same time.Also runs Satilite Dish.Iam Happy now.It gives me what I want.:wave
Hi...Just thought that I would throw this in......I use a 400 watt inverter from CTC to power the heater on my fridge. It works well. I use it while I`m towing and also for short periods when I`m parked but if I leave it on overnight it`ll drain my battery at about 3 in the morning and will start to beep because of the low input voltage so I just shut it off and switch to propane when I get up in the morning till I start driving again.....Benny
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