Well, what can I say Ron!!
You really make my day! Thank you!
The second box was a little bit hard to swallow and I did not assimilated all of it yet but I will.
But since you gave the final equations, it has been a piece of cake to make a spreadsheet to compute the values. Took me some time to figure out what was that bloddy 5,5V. I went to a false track assuming that it was the 6,5 volts minus the 1 volt of the wanted range. But wy! wy! wy!
Anyway! Let's see:
For the same meter, 392 Ohms, 0,842mA, Excel computing the voltage.
I want to monitor a range of 2 volts, from 7 to 9 volts. The Vin of the divider is still 12 volts and I want 0,5 volts as fine tuning (centering).
Without the centering Variable Resistor, R1 should be 3400 Ohms and R2 4760 Ohms.
The value computed for the VR is 680 Ohms. I dont know what is the nearest standard value so I will use a 500 Ohms for this example.
Then, with this 500 Ohms VR, the R1 give me 3150 Ohms and R2 4510 Ohms. So the nearest value would be 3,1K and 4,5K if these are standard values.
I you have a chance, could you confirm these figures.
Alain