RF/DC voltage calculation for quadrupole mass filter

In a quadrupole mass filter, U (DC) and V (RF) are the constant and alternating parts of the voltage applied between opposite rod pairs. They set the Mathieu parameters a and q, which decide which ion masses pass through. The values shown are the voltage between rod pairs, not the voltage of one rod relative to ground. You choose U and V from the target m/z, rod radius, and RF frequency to tune the filter.