Multi-phase, frequency coherent pulse width modulation signals are generated that maintain PWM data-set coherency regardless of user or system events. The method includes depositing a sample on a test strip at an application region, detecting a first detection signal arising from the test strip in the first detection zone, and generating a baseline for the first measurement zone by interpolating between values of the detection signal outside of the first measurement zone and inside of the first detection zone. The transactions are stored in many data structures. In further embodiments, a wafer edge ring is used to contain a liquid over a wafer active surface during a processing operation. In another embodiment, physical layer feedback is used for multicast mapping onto one or more unicast channels.