Saw sensor device using slit acoustic wave and method thereof

An SAW sensor device using a slit acoustic wave, comprising:

• a piezoelectric medium having a narrow slit which the slit acoustic wave passes through at its inside, and being divided into an upper portion and a lower portion from the narrow slit, for sensing liquid in the device;
• an input IDT formed at one side of the piezoelectric medium, for transducing an electric input signal into the slit acoustic wave;
• an output IDT formed at the opposite side to the input IDT in the piezoelectric medium, for receiving the propagated slit acoustic wave, and transducing the wave into an electric signal;
• an input liquid port for inputting the liquid into the narrow slit of the piezoelectric medium;
• and
• an output liquid port for outputting the liquid of the narrow slit of the piezoelectric medium.

A method for sensing an external pressure of an SAW sensor device, comprising the steps of:

• (a) when a thin membrane does not receive a pressure, calculating a frequency and velocity of electric signals of an input IDT and an output IDT in a narrow slit, and comparing the resultant values;
• (b) when the thin membrane receives an external pressure, calculating a frequency and velocity of electric signals of the input IDT and the output IDT, and comparing the resultant values;
• and
• (c) sensing intensity of the external pressure in consideration of velocity and frequency shifts due to the external pressure transmitted to the thin membrane,
• wherein step (c) for sensing the intensity of the external pressure is performed by previously setting frequency and velocity shift value data under the external pressure to an external device, and comparing the data values.

A method for sensing liquid of an SAW sensor device, comprising the steps of:

• (a) measuring a phase velocity of a slit acoustic wave proceeding in an empty slit, and calculating a frequency;
• (b) when the liquid flows in the narrow slit through an input liquid port, measuring a phase velocity of the slit acoustic wave in the narrow slit, and calculating a frequency;
• and
• (c) sensing dielectric permittivity and viscosity of the liquid passing through the narrow slit in consideration of velocity and frequency shifts.