Electromagnetic flowmeter can be classified in a variety of categories, according to the classification of excitation, according to the composition of sensors and converters classification, according to the classification of the connection according to the sensor and pipe connection method can also be classified according to use, this article mainly introduced by excitation classification The
1) DC excitation type. This kind of electromagnetic flowmeter is very small, only used to measure the flow of liquid metal, such as mercury at room temperature and high temperature liquid sodium, potassium and so on.
2) AC frequency excitation type. Early electromagnetic flowmeter with 50Hz frequency frequency of commercial excitation, due to susceptible to electromagnetic interference and zero drift and other reasons, has been gradually replaced by low-frequency rectangular excitation. However, in the measurement of mud, slurry and other liquid-solid two-phase flow, the low-frequency rectangular wave excitation method can not overcome the solid rubbed the electrode surface spikes, and frequency AC excitation instrument does not exist this shortcoming, so at home and abroad There are some electromagnetic flowmeter still use AC excitation mode.
3) low frequency rectangular wave excitation type. For low frequency rectangular wave excitation mode power consumption is small, zero stability, is the main electromagnetic flow meter excitation method. The waveform has "positive - negative" binary value and "positive - zero - negative - zero" three - value two. Some three smooth electromagnetic flowmeter excitation frequency can be set by the user, the general small diameter meter with a higher frequency, large diameter meter with a lower frequency.
4) Dual frequency excitation type. The current of the excitation current is to super high frequency rectangular wave on the low frequency rectangular wave, mainly to overcome the existence of slurry noise and flow noise of the binary rectangle wave excitation, and improve the stability and response characteristics of the instrument.