Patent ID: 8601857

Claim:
A measurement method that uses a crystal oscillator, wherein the method comprises: contacting a material to be measured to the crystal oscillator and oscillating the crystal oscillator that includes electrodes formed on both surfaces of a piezoelectric plate, and an uneven-surface formed either on one of the electrodes disposed on the side in contact with the material to be measured, or on a detector formed on the electrode; and measuring an amount of change in frequency (f 2 ) that corresponds to the high-frequency side of two frequencies that represent a half value of a conductance maximum value of the crystal oscillator, so as to measure a density of the material, wherein amounts of change of at least two of the frequencies on an admittance circle diagram of the crystal oscillator are measured to also measure a viscosity of the material, and wherein said at least two frequencies on the admittance circle diagram are any two of frequencies (f 1 , f 2 ) that represent the half value of the conductance maximum value of the crystal oscillator, and a resonant frequency (fs) of the crystal oscillator.