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DC Volt Meter

Yahoo Message Number: 17918
Has anyone found a source for a plug in the cigarette lighter device that will read out battery voltage Digitally for use on the RV ???

Ron and Molly, '01 Intrigue # 11262, San Diego

Re: DC Volt Meter

Reply #1 –
Yahoo Message Number: 17919
I bought one at Radio Shack when I was having some car battery problems earlier this year. It's digital and according to my multimeter it was accurate.
Bob

'05 Intrigue LE #11872

Re: DC Volt Meter

Reply #2 –
Yahoo Message Number: 17923
From: Bodie6413@...>

Quote
Has anyone found a source for a plug in the cigarette lighter device that > will read out battery voltage Digitally for use on the RV ???
I found one, made by Nordskog, at http://tinyurl.com/cmufr . Pricey, but worth it. I ordered ours direct from the company.

Dick (& Geri) Campagna
'98 36' Intrigue #10571
Mfd: 11/97

Re: DC Volt Meter

Reply #3 –
Yahoo Message Number: 17924
From: "Bob Stephens" af9w@...>

Quote
>I bought one at Radio Shack when I was having some car battery > problems earlier this year. It's digital and according to my > multimeter it was accurate.
Serious question: How do we know if our multimeters are accurate?

Dick (& Geri) Campagna
'98 36' Intrigue #10571
Mfd: 11/97

Re: DC Volt Meter

Reply #4 –
Yahoo Message Number: 17925
You don't.

We send our meters (lab meters) in every year or so and get them calibrated. It also depends on the quality of the meters of course.

For RV use, I guess I wonder why it even matters. Plus or minus a few percent is not going to mess up your troubleshooting much.

John and Terry
2005 Affinity

Quote from: Dick Campagna

Re: DC Volt Meter

Reply #5 –
Yahoo Message Number: 17952
Since we are only RV'ing and not launching space shuttles, close counts.
Bob

Quote from: Dick Campagna

Re: DC Volt Meter

Reply #6 –
Yahoo Message Number: 17969
From: "Bob Stephens" af9w@...>
Dick Campagna wrote ...

Quote
>> Serious question: How do we know if our multimeters are accurate?

Since we are only RV'ing and not launching space shuttles, close > counts.
But when performing an open circuit voltage test on the batteries when dry camping using the inverter, for example, isn't meter accuracy important to help make sure I'm not discharging the batteries too much? An inaccuracy of a few tenths can make a big difference. Some of us have to depend on auxiliary meters 'cause of inadequate standard instrumentation. And, even then, standard instrumentation may be inaccurate, too!

Dick (& Geri) Campagna
'98 36' Intrigue #10571
Mfd: 11/97

Re: DC Volt Meter

Reply #7 –
Yahoo Message Number: 17974
Dick

There are two factor involved in this question. One is the meter's accuracy and the other is the meter's precision. They are not the same but both effect your concern. The accuracy is the ability to return to the same point on the scale each time the meter is presented a know standard voltage. This is where the quality of the materials come in to play or the analog to digital conversion process. Precision is the ability to determine what the actual reading is. Here things like the size of the scale, the width of the pointer and hash marks and how precisely they have been placed on the meter or, in the case of digital, how many digits are displayable. So a meter can be very accurate but not very precise or vice versa. To obtain both great accuracy and high precision of course directly increases the cost and complexity of the meter. Usually the more accurate and precise a meter is the more delicate it becomes and subject to heat and humidity variations and vibration.
The average multi-meter is not really very accurate in it's ability to match a known standard but does reasonably well at providing the same reading each time the known voltage is read. Usually the accuracy of a meter is quoted in the paperwork that cmes with it. They are really more intended to read relative changes rather than exact values to compared to manufactures ratings. Batteries themselves will produce a range of values when fully charged and the manufacturer is faced with providing typical range values. A multi-meter should be readable to 1 tenth of a volt in most cases. If you really want to use a multimeter to check the accuracy of the inverter readings then fully charge the battery using a hygrometer (another whole set of accuracy/precision questions) and read the voltage. In the future, either offset your readings from the manufacture's ratings by the difference to determine % of charge or recalibrate the meter.
My Zantrex displays DC voltage to the 10th of a volt and I am betting on it as a better reading than my multimeter although I have not made a comparison. I have Auto Genstart so I rely on the fact that Zantrex is not going to risk replacing batteries because their voltage sensing circuitry was too inaccurate. Of course that is a trust that I could pay dearly for some day.
There is an old story of a young fellow who was having great deal of trouble understanding the concept that mathematically zero cannot be the result of dividing two real numbers. In frustration his teacher said 'Tom your girlfriend Sue lives 3 miles across town from you house. If you started out and kept dividing the distance in half would you ever get to Sue?' 'No said Tom but before very long I would be close enough for all practical purposes'. Unfortunately that's the ball game with meter accuracy and precision.

Don Seager

2004 Allure 31046

Re: DC Volt Meter

Reply #8 –
Yahoo Message Number: 17977
If you are worried about accuracy I would suggest going to a marine store and purchasing a good DC voltmeter that you can add to the coach. Most marine guys spend less time on shore power than we do and use pretty quality stuff. Here is a link to one of the better companies who makes meters for boats http://www.bluesea.com/default.asp. Their analog meters are +/-3% of full scale so for instance their analog voltmeter has a scale range of 8-16 so that would be .24 of a volt. Their digital meters are accurate to +/-.5% of reading or as their footnote says +/1 1 least significant digit which is 1 hundredth of a volt. On a 12volt scale. Voltmeters are pretty easy to install.

Bob

'05 Intrigue LE #11872

Quote from: Dick Campagna
> From: "Bob Stephens"
Dick Campagna wrote ...

>> Serious question: How do we know if our multimeters are

accurate?

Quote
>

> Since we are only RV'ing and not launching space shuttles, close > > counts.

But when performing an open circuit voltage test on the batteries

when dry

Quote
camping using the inverter, for example, isn't meter accuracy

important to

Quote
help make sure I'm not discharging the batteries too much? An
inaccuracy of

Quote
a few tenths can make a big difference. Some of us have to depend

on

Quote
auxiliary meters 'cause of inadequate standard instrumentation.

And, even
 

Re: DC Volt Meter

Reply #9 –
Yahoo Message Number: 17979

I was involved for years in professional technical service on electronic equipment. The best digital meters around are made by Fluke. They are accurate, precise and durable.

> But when performing an open circuit voltage test on the batteries when dry
Quote
camping using the inverter, for example, isn't meter accuracy
important to

Quote
help make sure I'm not discharging the batteries too much? An
inaccuracy of

Quote
a few tenths can make a big difference. Some of us have to depend
on
Quote
auxiliary meters 'cause of inadequate standard instrumentation.
And, even

Quote
then, standard instrumentation may be inaccurate, too! > > Dick (& Geri) Campagna > '98 36' Intrigue #10571 > Mfd: 11/97
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