 Mag meters can also be useful for measuring raw (untreated/unfiltered) water and waste-water since there is no mechanical measuring element to get clogged or damaged by debris flowing through the meter.Strainers are not required with mag meters since there is no measuring element in the stream of flow that could be damaged.Since stray electrical energy flowing through the flow tube can cause inaccurate readings, most mag meters are installed with either grounding rings or grounding electrodes to divert stray electricity away from the electrodes used to measure the flow inside the flow tube.