Differential Bias Resistors

My UUT puts out a 15 v spike...about 1 msec in duration that I need to measure differentially.  I think my measurement sw is set correctly.  If the circuit looks like the attached file do I still need to add the bias resistors??  The 12 ohms is the load.  The 47k's and 10k are voltage dividers.  10:1.

Thanks..