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I have a chilled water heat exchanger used to cool oil in a gearbox, From the energy balance equation: mdot_water * cp_water *deltaT_water = mdot_oil * cp_oil * deltaT_oil. Re-written, this becomes: (mdot_water/mdot_oil) * (cp_water/cp_oil) = deltaT_oil/deltaT_water =...

Thank you for clearing that up IRstuff. So, re-arranging the voltage divider equation, the internal resistance can be determined from Ri=Re(Vin/Vout-1) This would put the internal resistance of the battery 10*(3/2.85-1) = .52 ohms and that of the orange at 10*(.89/.1-1)=79 ohms. I guess it...

Thank you for the suggestion to use resistors instead of flashlight bulbs. I picked up 4 10ohm power resistors. Now I have another set of questions.... When I connect the DMM across a battery carrier holding 2 AA batteries, I get the expected 3V. However, when I connect it across a 10 Ohm power...

Thank you OperaHouse, For a long time I was getting incorrect readings. It turned out that my reference was 5.07V. I like the idea of averaging before writing. Since you have some experience with the UNO, have you ever tried taking a voltage differential? When I did it, I got random values...

Thanks for the tip Benta.

Thank you for your response IRstuff. Are you saying that the intent of the tests is not compromised because each battery/light pairing forms its own independence circuit even though the negative terminals of each battery is connected to the computer's ground?

I'm helping my son with his science fair project to compare the useful lives of different batteries. I helped him build a data logger using an Arduino micro controller board which as 6 Analog Input channels (the board is powered via the host computer's USB port). Originally, the circuit was...