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PostPosted: Tue May 17, 2011 2:32 am 
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Joined: Thu Feb 25, 2010 12:57 pm
Posts: 58
Hello,
Id like to use the analogic gauge to moniter voltage.

To do this, and not fry the gauge, I need to set up a voltage divider. No problem, thanks to Kirtchoff.

I would just simply use a resistor with twice the impedance of the analogic's analog input in series with the analog input. That way an input of 15 VDC will be felt as 5 VDC on the analogic.

So with a Slope of 3 and an intercept of 0 it would work, as long as the voltage doesn't exceed 15vdc. Since I plan on using this in my computer to monitor voltages seprate from the computer's internal sensors and software (that way I know what its doing if my computer goes on the frits)
15VDC would be a good top out voltage.

So now I need a very important peice of information,

What is the input impedance of the analogic's Analog inputs?
Thank you


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PostPosted: Tue May 17, 2011 2:52 am 
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Joined: Thu Feb 25, 2010 12:57 pm
Posts: 58
Also
Just remembered that computers use Negitive and Positive voltages.

Also rememerd that all 4 analog inputs use a - and a + for each input.

Can Analogic handle a floating ground?

IE: If I use 1 power source with no common ground to the computer to power the gauge's 12 VDC source power,

Then use analog 1 for 0 - 5 VDC by hooking up the - side to chassie, then the + side to the resistor block.

Would it then also work for useing analog 2 for example, useing the - to the resistor block for the - power source, then the + to the chassie. that way Polarity is preserved, however the analog 1, analog 2, and Analogic are all have diffrent grounds.

Of course for analog 2 id have to set the slope to -3 instead of 3.


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PostPosted: Tue May 17, 2011 2:02 pm 
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Joined: Sat Aug 25, 2007 7:28 am
Posts: 267
OK. the analog channels are all referenced to the 12VDC negative that powers the analogic. Any signal in must also be referenced to this ground. The signals in can only be 0 to +5VDC no negative going signal will be read. The input Z of the analogic is 47K. To monitor 15V I would simply use a string of 3 same valued resistors (make the total current around 1 or 2 ma 4.7K works pretty well on paper) monitor the voltage drop on 1 resistor and then multiply by 3 for the actual 15V measurement.


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PostPosted: Tue May 17, 2011 9:55 pm 
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Joined: Thu Feb 25, 2010 12:57 pm
Posts: 58
Thank you, that information is very helpful :)
The rest is just math.
Thanks :)
-Jonathan


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PostPosted: Sat Apr 16, 2016 1:46 pm 
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Joined: Sat Apr 16, 2016 1:33 pm
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insylem wrote:
Thank you, that information is very helpful :)
The rest is just math.
Thanks :)
-Jonathan

im assuming this worked, a shame the gauge cant read the incomin power itself.


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PostPosted: Mon Apr 18, 2016 7:31 am 
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Joined: Wed Aug 22, 2007 7:02 pm
Posts: 4673
Location: Avon, OH
Yes it did. We have what we call a voltage sensor now for $20 that does this. It's not on our website, was there but must have been omitted in last update, so I could send a paypal invoice if you want one. Converts 12v signals to proportional levels below 5.

Todd

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