A magnetic flowmeter comprising: a pipe having a non-conductive liner on an inner surface; a field coil adjacent to the pipe and configured to generate a magnetic field across a fluid flowing through the pipe; a first electrode located in a first tunnel passing through the pipe and into the non- conductive liner , and a second electrode located in a second tunnel passing through the pipe and into the non-conductive liner , the first electrode and the second electrode configured to sense a voltage induced by the magnetic field across the fluid flowing through the pipe ; a first sealed compartment attached to an outer surface of the pipe , the first sealed compartment enclosing at least one of the field coil ,the first electrode, and the second electrode; a first MEMS relative humidity probe or sensor located within the sealed compartment and configured to sense relative humidity in the first sealed compartment; and an electronics compartment having transmitter circuitry connected to the field coil , the first electrode , the second electrode , and the first MEMS relative humidity probe or sensor , wherein, the first sealed compartment comprises a magnetics compartment surrounding the pipe and enclosing the field coil ,the first electrode, the second electrode, and the vapor sensor, wherein the transmitter circuitry generates a first output representing a flow rate of the fluid as a function of the voltage sensed by the first electrode and the second electrode , and generates a second output based upon the relative humidity sensed by the first MEMS relative humidity probe or sensor , the second output providing an alert indicating vapor permeation in the first sealed compartment to prompt a user to replace the magnetic flowmeter when a threshold level of humidity is sensed in the first sealed compartment. a pipe having a non-conductive liner on an inner surface; a field coil adjacent to the pipe and configured to generate a magnetic field across a fluid flowing through the pipe; a first electrode located in a first tunnel passing through the pipe and into the non- conductive liner , and a second electrode located in a second tunnel passing through the pipe and into the non-conductive liner , the first electrode and the second electrode configured to sense a voltage induced by the magnetic field across the fluid flowing through the pipe ; a first sealed compartment attached to an outer surface of the pipe , the first sealed compartment enclosing at least one of the field coil ,the first electrode, and the second electrode; a first MEMS relative humidity probe or sensor located within the sealed compartment and configured to sense relative humidity in the first sealed compartment; and an electronics compartment having transmitter circuitry connected to the field coil , the first electrode , the second electrode , and the first MEMS relative humidity probe or sensor , wherein, the first sealed compartment comprises a magnetics compartment surrounding the pipe and enclosing the field coil ,the first electrode, the second electrode, and the vapor sensor, wherein the transmitter circuitry generates a first output representing a flow rate of the fluid as a function of the voltage sensed by the first electrode and the second electrode , and generates a second output based upon the relative humidity sensed by the first MEMS relative humidity probe or sensor , the second output providing an alert indicating vapor permeation in the first sealed compartment to prompt a user to replace the magnetic flowmeter when a threshold level of humidity is sensed in the first sealed compartment. <EOS>