  A number of modern millimeter, sub-millimeter, and far-infrared detectors are
read out using superconducting microwave (1-10GHz) resonators. The main
detector technologies are Transition Edge Sensors, read out using Microwave
SQUID Multiplexers ($\mu$mux) and Microwave Kinetic Inductance Detectors. In
these readout schemes, sky signal is encoded as resonance frequency changes.
One way to interrogate these superconducting resonators is to calibrate the
probe tone phase such that any sky signal induced frequency shifts from the
resonators show up primarily as voltage changes in only one of the two
quadratures of the interrogation tone. However, temperature variations in the
operating environment produce phase drifts that degrade the phase calibration
and can source low frequency noise in the final detector time ordered data if
left to drift too far from optimal calibration. We present a method for active
software monitoring of the time delay through the system which could be used to
feedback on the resonator probe tone calibration angle or to apply an offline
cleaning. We implement and demonstrate this monitoring method using the SLAC
Microresonator RF Electronics on a 65 channel $\mu$mux chip from NIST.
