Timeline for Simple DC voltage scaling with two ranges, lower range voltage limited
Current License: CC BY-SA 3.0
7 events
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| Oct 10, 2013 at 7:15 | comment | added | Andy aka | @TimMartin try that now. I just upvoted your question - it might be enough. You can "accept" any answer but i'd wait for a day to see if anyone comes up with alternative ideas. | |
| Oct 9, 2013 at 23:58 | comment | added | Tim Martin | Since I am new, my reputation score is not sufficient to upvote your answer... however your information is indeed helpful. | |
| Oct 9, 2013 at 17:53 | comment | added | Andy aka | That's about it in a nutshell. The opamp is configured as non-inverting gain of ten. It also offers protection to the micro. Consider upvoting the answer if you feel it helpful. | |
| Oct 9, 2013 at 17:47 | comment | added | Tim Martin | Thanks for the input Andy. If I understand… the op-amp is used to amplify the lower end of the main voltage divider resulting in a wider range being fed to the second ADC. I'm new to this stuff so I'll look up the data sheet on the AD8605 and then see how to hook it into the circuit. I'm anticipating that the amplification (gain?) is determined by selecting appropriate resistors… and the top-end output of the op-amp is dictated by the rail supply voltage (5V). I guess it's time to dive in again! | |
| Oct 9, 2013 at 15:12 | comment | added | Andy aka | @TimMartin OK then I'd use an op-amp with gain of ten tied to the same voltage divider. Op-amp feeds spare input and there should be no problem. AD8605/6 is my recommendation for a good rail-to-rail workhorse op-amp but there are several that will do and there's probably some very low offset voltage devices that would work really good with extremely low error. | |
| Oct 9, 2013 at 15:04 | comment | added | Tim Martin | Thanks for the response. I'm using an arduino with the ATmega328 micro. Yes, it is 10-bit resolution. I had already implemented an averaging procedure using 16 and 32 sample arrays and it did indeed help with the inherent noise. I'd still like to see better resolution in the low voltage range. Inexpensive multimeters seem to do this when selecting measurement scale. If I select a 20 volt DC scale, the meter simply indicates an error if a 100V potential is attempted. | |
| Oct 9, 2013 at 8:01 | history | answered | Andy aka | CC BY-SA 3.0 |