Description of the characteristics of the electromagnetic flowmeter excitation method

(1) DC excitation type
This type of electromagnetic flowmeter is small in number and is only used to measure the flow rate of liquid metal, such as mercury at normal temperature and liquid sodium and potassium at high temperatures.
(2) AC power frequency excitation type
The earlier electromagnetic flowmeter was excited by 50 Hz power frequency mains. Due to its vulnerability to electromagnetic interference and zero drift, it has been gradually replaced by low frequency rectangular excitation. However, when measuring liquid-solid two-phase flow such as mud and slurry, the low-frequency rectangular wave excitation method can not overcome the spike noise generated by solid rubbing on the surface of the electrode, while the power frequency AC excitation meter does not have this disadvantage, so there are still Some electromagnetic flowmeters still use AC power frequency excitation.
(3) Low-frequency rectangular wave excitation type 1 Since the low-frequency rectangular wave excitation method has low power consumption and good zero-point stability, it is the main excitation mode of the current electromagnetic flowmeter. Its waveform has two values: “positive one negative” and “positive one zero one minus one zero”. Some electromagnetic flowmeter excitation frequency can be set by the user. Generally, small-diameter instruments use higher frequencies, and large-diameter instruments use lower frequencies.
(4) Dual frequency excitation type
The waveform of the excitation current is a high-frequency rectangular wave superimposed on the low-frequency rectangular wave. It mainly overcomes the slurry noise and flow noise existing in the excitation of the binary rectangular wave, and improves the stability and response characteristics of the meter. Therefore, it is widely used in pulp, paper and sewage. Processing and other industries.