Difference between two-wire and four-wire electromagnetic flowmeters

Four-wire electromagnetic flowmeter - four-wire system is the traditional electromagnetic flowmeter output signal line and power line (or magnetic flux wire between the flow sensor and sensor) consists of two sets of two wires of the four-wire system, is currently The main format. Two-wire electromagnetic flowmeters - current temperature, pressure/differential pressure, flow and level parameters, field instruments tend to develop two-wire instrumentation for output signals and power common conductors. Two-wire instruments do not require mains power, while electromagnetic flowmeters are often installed in remote locations where there is no mains supply. The use of a two-wire system can save the cost of utility wiring. The design idea of ​​the two-wire electromagnetic flowmeter power supply is divided into zero-signal output current (ie, 4mA) supply, greater than zero-signal output supply, and battery (or solar cell) supply. Battery-powered electromagnetic flowmeters and electromagnetic water meters are suitable for installation in difficult places such as city distribution pools or discharge points after sewage treatment in the suburbs. Some models have a battery life of 1-2 years, and some are as long as 8 to 10 years.