AWWA C751:2019 pdf download.Magnetic Inductive Flowmeters
Magmeters will operate reasonably well even in applications where they are oversized or undersized. Many vendors provide options such as displays, totalizers, multiple outputs, and the ability to measure bidirectional flow conditions to fit the most demanding applications.
4.3.3 Electrodes. One or more pairs of contacts are used to detect the induced voltage. Each of the contacts is a small round metal rod approximately 1–1 in. (3–6 mm) in diameter sealed at the liner and exposed to the process liquid that measures the voltage in the liquid. Typically, the electrodes are made of type 316 stainless steel or high nickel content alloys (e.g., Hastelloy or others), but other conductive metals could be used.
4.3.4 Coils. A pair of wound wire coils (rectangular or other shapes) on opposite sides of the flow tube are most often installed at the outside of the flow tube, with some models installed inside. When current is applied to the two coils, a magnetic field is generated, permeating the flow cross section of the measuring tube.
4.3.5 Secondary device/electronic transmitter (converter). The electronic component of the magmeter will typically include a microprocessor that converts the voltage to both a digital and an analog signal proportional to the velocity of the liquid in the flow tube to display and to record the flow rate/total flow results in engineering units specified by the user. It also supplies a controlled current to the coils to generate the magnetic field. The converter typically provides an analog and a pulse output signal.
4.3.6 Grounding device (rings/electrodes). The purpose of a ground device (grounding rings or grounding electrodes) is to short any stray electrical potential in the process liquid to earth ground so the stray electrical potential does not pass through the meter and cause noisy and inaccurate readings. A ground device is only mandatory when mounting the meter in lined process pipes or nonconductive pipes (e.g., plastic or PVC), but some manufacturers may recommend its use in the water supply lines. The most common grounding device is a pair of rings installed between the flowmeter flanges and the process piping flanges, which are electrically grounded, to earth ground. The grounding ring inner diameter is in contact with the process liquid.AWWA C751 pdf download.