adding two differential voltage from voltage divider

[haye]

Hi,

A very basic question, I have a DC voltage to measured but it is out of 10V range of my PCI-6221 DAQ which is around 11.9V. If I use a simple voltage divider (I use high resistance to avoid current leaking) 560k and 560k Ohm resistors (both 1% tolerance), is it wise to measure voltage individually at each of resistor and then sum it up? BTW I configured both of the channel to differential. When I did this, roughly I got voltage reading 5.96 and 6.19 volts i.e. different value and when add together it is higher than the 11.9 V.

OR

Should I just measure one reading and simply times by 2 (the ratio from the voltage divider).

Tried to search "adding two differential voltage" keyword before but couldn't find the answer to this.

Hopefully someone can get some benefit from this basic question.

Kindest regards,

Haye

[crossrulz]

I have had a lot of success just reading the last resistor in the divider.  You can then setup a DAQmx scale to automatically apply the x2 to get your true voltage out of the DAQmx Read VI.