Apparatus and associated methods relate to a Metered-Commodity Consumption Meter (MCCM) utilizing a rotationally occluded optical beam to simultaneously measure flow/consumption and verify operational integrity. In accordance with an exemplary embodiment, an existing MCCM may be retrofit by sealably attaching a module containing an optical system which may generate one or more optical beams. Each optical beam may have a defined optical path originating from an optical source and terminating at an optical sensor within the module. In an exemplary embodiment, a Rotational Retrofit Member (RRM) may be attachable to a rotational metering gear responsive to a flow/consumption of the metered commodity. The RRM may have an occluding blade which may partially occlude the optical beams periodically when the RRM rotates. In various embodiments, the MCCM may be retrofit to make the measurement of the metered commodity impervious to external magnetic fields.
