Hey guys. I posted this question on Y!A but no one has answered it yet... I guess this is a more appropriate place to ask.
Suppose I have a DC power source (a solar array) that can output up to 110V & 40A, and I want to log the voltage produce by the panel throughout the day. Since feeding 110V directly into the analog input pin of my data-logger will damage it, I am going to scale down the voltage to a maximum of 4.5V. Also, I want to minimize power dissipation by the two resistor, so I am going to use 2 high resistance resistor (maybe 1MegaOhm and 40kOhm) // with the panel, so that a tiny amount of current can flow through the resistors.
But, I heard that high resistance voltage divider is not going to give high precision voltage output. My question is - is it possible to use a lower resistance values resistors with an op amp in voltage follower configuration to yield high precision and low power dissipation voltage divider, considering an OpAmp has Infinite input impedance?
According to this site, one of the application is that "A bridge circuit or a voltage divider circuit - maybe where there is a resistive sensor in the bridge or voltage divider - and drawing current when you measure the voltage would be enough to change the voltage." http://www.facstaff.bucknell.edu/mastascu/elessonsHTML/OpAmps/OpAmp3Note1Buffer.htmlBut I am not sure how exactly do I setup the circuit and what resistor to use. There was another guy who suggested me to use an instrumentation amplifier instead of an OpAmp, but I can't figure out what difference is it going to make.
I guess using an OpAmp also has another advantage - in order to measure the voltage from the voltage divider, I am going to have to connect the ground of the 110V solar panel with the ground pin of my tiny microcontroller. If my voltage divider has infinite impedance, it can effectively eliminate ground loop effect. Can anyone confirm this? Thanks!