Method for sensing conductivity and flow rate of a liquid in a tube

Abstract

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 makes the exciting-current generating device to generate an exciting current when the switch is connected to the flow-sensing device. The microprocessor makes the exciting-current generating device to stop generating exciting current and computing conductivity of liquid when the switch is electrically connected to the voltage-amplitude conductivity-sensing device.

What is claimed is: 
     
         1 . A method for sensing conductivity and flow rate of a liquid in a tube, comprising:
 (a) generating a sine oscillation voltage pulse;   (b) calculating a conductivity via the sine oscillation voltage pulse;   (c) determining whether the conductivity is smaller than a predetermined value;   (d) determining whether a tube is empty;   (e) after the step (d), adjusting current value of a constant current; and   (f) sensing flow rate of the liquid.   
     
     
         2 . The method of  claim 1  for sensing conductivity and flow rate of a liquid in a tube, wherein the step (b) comprises:
 (b1) calculating an impedance value via the sine oscillation voltage pulse; and 
 (b2) calculating the conductivity via the impedance value.