Electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube
An electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube includes a first microprocessor, a transducer, flow-sensing device, an exciting-current generating device, a voltage-amplitude conductivity-sensing device, and a switch. The transducer includes coils and sensing electrodes. The switch is electrically connected to the first microprocessor and the sensing electrode. The switch is selectively connected to the flow-sensing device or the voltage-amplitude conductivity-sensing device according to the signals sent from the microprocessor. The microprocessor drives the exciting-current generating device to generate an exciting current when the switch is connected to the flow-sensing device. The microprocessor stops the exciting-current generating device from generating exciting current and computing conductivity of liquid when the switch is electrically connected to the voltage-amplitude conductivity-sensing device.
1. An electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube, comprising:
a first microprocessor;
a transducer, comprising two coils and two sensing electrodes;
an exciting-current generating device, electrically connected to the first microprocessor and the coils;
a flow-sensing device, electrically connected to the first microprocessor;
a voltage-amplitude conductivity measuring device, electrically connected to the first microprocessor; and
a switch, electrically connected to the sensing electrodes, the first microprocessor, the flow-sensing device, and the voltage-amplitude conductivity measuring device;
wherein the switch makes an electrical connection between the sensing electrodes and the flow-sensing device or the sensing electrodes and the voltage-amplitude conductivity measuring device according to a signal sent by the first microprocessor, the first microprocessor is configured to drive the exciting-current generating device to generate an exciting current when the sensing electrodes and the flow-sensing device are electrically connected so as to calculate flow rate of the liquid, and the first microprocessor is configured to stop the exciting-current generating device from generating the exciting current when the sensing electrodes and the voltage-amplitude conductivity measuring device are electrically connected so as to calculate conductivity of the liquid.
2. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 1 , wherein the voltage-amplitude conductivity measuring device comprises:
a differential amplification module, electrically connected to the first microprocessor and the sensing electrodes;
a voltage division resistor, electrically connected to the differential amplification module and the sensing electrodes; and
an oscillating module, electrically connected to the voltage division resistor and configured to generate a sinusoidal signal;
wherein the sensing electrodes are immerged in the liquid, the sensing electrodes and the liquid generate an inductive impedance together, the differential amplification module outputs a sinusoidal signal divided by the inductive impedance and the voltage division resistor and outputs a half-sine wave signal to the first microprocessor, and the first microprocessor calculates the conductivity of the liquid.
3. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 2 , wherein the oscillating module comprises an operational amplifier, a positive feedback unit and a negative feedback unit, the operational amplifier comprises an inverting input end, a non-inverting input end and an output end, the positive feedback unit is electrically connected to the non-inverting input end and the output end, the negative feedback unit is electrically connected to the inverting input end and the output end.
4. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 3 , wherein the positive feedback unit comprises a RC parallel network and a RC series network, and the RC parallel network is electrically connected to the non-inverting input end of the operational amplifier, and the series network is electrically connected to the non-inverting input end and the output end of the operational amplifier.
5. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 4 , wherein the RC parallel network comprises a first resistor and a first capacitor, one end of the first resistor is electrically connected to the non-inverting output end, another end of the first resistor is electrically connected to the ground, the first capacitor and the first resistor are connected in parallel, the RC series network comprises a second resistor and a second capacitor, one end of the second resistor is electrically connected to the non-inverting input end of the operational amplifier, another end of the second resistor is electrically connected to one end of the second capacitor, and another end of the second capacitor is electrically connected to the output end of the operational amplifier.
6. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 5 , wherein the negative feedback unit comprises an input resistor and a feedback resistor, the input resistor is electrically connected to the inverting input end of the operational amplifier and the ground, and the feedback resistor is electrically connected to the inverting input end and the output end of the operational amplifier.
7. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 6 , wherein the negative feedback unit further comprises a first diode and a second diode, anode of the first diode is electrically connected to the inverting input end of the operational amplifier, cathode of the first diode is electrically connected to the output end of the operational amplifier, anode of the second diode is electrically connected to the output end of the operational amplifier, and cathode of the second diode is electrically connected to the inverting input end of the operational amplifier.
8. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 2 , wherein the differential amplification module comprises an operational amplifier, a third resistor, a fourth resistor, a fifth resistor and a sixth resistor, the operational amplifier comprises an inverting input end, a non-inverting input end and an output end, the third resistor is electrically connected to the non-inverting input end of the operational amplifier and the voltage division resistor, the fourth resistor is electrically connected to the non-inverting input end of the operational amplifier and the ground, the fifth resistor is electrically connected to the inverting input end of the operational amplifier, the sensing electrode and the ground, and the sixth resistor is electrically connected to the inverting input end and the output end of the operational amplifier.
9. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 1 , wherein the exciting-current generating device comprises a current regulating unit, a first switching element, a second switching element, a third switching element and a fourth switching element, the current regulating unit is electrically connected to the first microprocessor, the first switching unit, the second switching unit, the third switching unit and the fourth switching unit.
10. The electromagnetic flowmeter with voltage-amplitude conductivity-sensing function for a liquid in a tube of claim 9 , wherein the exciting-current generating device further comprises a coil anomaly detection, and the coil anomaly detection is electrically connected to the first microprocessor, the current regulating unit, the third switching unit and the fourth switch unit.