Is Power Dissipation of the Flowmeter Important?
2019-06-11
Yes. The excitation currents for electromagnetic flow meters can be quite large, from up to 50 mA for smaller diameters up to 500 mA or 1 A for larger diameter pipes. The constant current circuit can consume significant amount of power and board area when it’s linearly regulated.
A switch-mode power supply can be used to save the power dissipated compared to the linear regulated constant current circuit. As shown in the diagram, is configured in the constant current source output mode.
The 1.2 V output voltage is divided by two resistors to 150 mV. This 150 mV voltage is applied to the voltage track pin so that voltage feedback pin also be kept to 150 mV. When putting a 0.6 Ω current set resistor at the feedback pin, it will adjust its output current to its ISET level. By adjusting the value of the current setting resistor connected to the feedback pin, the constant current source can be tuned.