Re: impedance bridge, which one is better?

I will probably use a resistor divider to convert the negative voltage to positive, like described here https://www.edaboard.com/thread285737.html#post1224998 I like this solution, provided that the vcc is stable and the resistors are of low ppm I believe greater accuracy can be achieved without the temperature variation problems. Of course you have some voltage loss from the divider but in my application comparative readings have to be made and not actual. More important, is the immunity to variations of the measuring equipment, to ensure that the same readings will always represent the same values.
Having that in mind, I would like to make a potential divider but I do not know the short of resistor values to use, that is why I am asking about the impedance at the monitor and dc out ports.
Any suggestions will be appreciated.