I mean that with a divider of 2.2k + 10k, 10V at the midpoint corresponds to 
12.2V across the entirety. Similarly, 4.7k+10k will give you 14.7 / 10 * 10V = 
14.7V range (10V at midpoint is 14.7V across entirety). 

C



> On Feb 21, 2015, at 11:53 AM, Peter Hollenbeck <pwhb...@gmail.com> wrote:
> 
> Colin,
> Sorry about my feeble attempt at ASCII art. My divider consists of two 
> connected 1K resistors. Battery plus and minus are connected at the ends. 
> MS-TV red wire connected at the center. MS-TV black wire connected at same 
> place as battery minus.
> 
> I will try your suggestion. What do you mean "a range of 12.2V"?
> The battery bank voltage will range from about 11 to 13.5 so that is the 
> range I would like to measure.
> Thanks,
> Peter
> 
> 
> 
>> On Sat, Feb 21, 2015 at 11:40 AM, Colin Reese <colin.re...@gmail.com> wrote:
>> I unfortunately cannot read your ascii art, which in itself is disappointing.
>> 
>> 2k is a bit low for a divider - you'll get standby current of 6mA. You 
>> should also try optimizing the split to fit the range you can measure. So 
>> you'd want a ratio of R2/Rtotal =measured range/ measurable range. So 
>> 2.2k/10k would give you standby of <1mA and a range of 12.2V.
>> 
>> As for diagnosing your actual problem, I'd get out a meter or scope to 
>> determine which end your issue is on.
>> 
>> Colin
>> 
>> 
>> 
>> 
>> > On Feb 21, 2015, at 11:29 AM, Peter Hollenbeck <pwhb...@gmail.com> wrote:
>> >
>> > I am using a LinkUSB and an MS-TV to read voltage from a 12 volt system. 
>> > The MS-TV is limited to 10 volts so a made a voltage divider. I know next 
>> > to nothing about electronics. Two weeks ago, with a test 12v power supply 
>> > I played with various resistor values, from 1K to 1M. The 1K resistors 
>> > appeared to give the best reading, about 6 volts. The higher the value the 
>> > lower the output. Now, working with a real 12v battery system I am getting 
>> > values ranging all over - .1, .82, .07, 10+, and rarely something 
>> > reasonable, like 6.6.Within several minutes I just got 0.7 followed by 
>> > 9.75. An inverter connected to the battery bank displays 12.1 volts and 
>> > the output from my program shows .71 volts.
>> >
>> > My divider looks like this:
>> >
>> >                             1K               1K
>> >        ---------^v^v------------^v^v-----------------------
>> >        |                    |                  |                |
>> >        |                    |                  |                |
>> >        |                    |                  |                |
>> >        |                    |                  |                |
>> >  battery (+)              |                  |           battery (-)
>> >                       MS-TV          MS-TV
>> >                       red wire        black wire
>> >
>> > I sure would appreciate suggestions.
>> > Thank you,
>> > Peter
>> >
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