초록 ▼

A method and apparatus for measuring the natural resonant frequency of a spring element by monitoring a phase difference between an output signal from the spring element and an input signal to the spring element and by adjusting frequency of the input signal until a detected phase difference signals

A method and apparatus for measuring the natural resonant frequency of a spring element by monitoring a phase difference between an output signal from the spring element and an input signal to the spring element and by adjusting frequency of the input signal until a detected phase difference signals that the natural resonant frequency has been reached. The method and apparatus are applied to a micro-cantilevered elements used to measure gas compositions and concentrations. Such elements are provided with coatings that absorb gas to cause deflections and changes in the mass or spring constant of the cantilevered element. These changes correspond to changes in the natural resonant frequency of the cantilevered element which are measured using the method and apparatus described herein.

대표청구항 ▼

[ I claim:] [1.] A method for measuring a natural resonant frequency of movement of a spring element, the method comprising:causing vibratory movement of the spring element;applying an electrical input signal of adjustable frequency and variable phase from a voltage controlled oscillator to a transd

[ I claim:] [1.] A method for measuring a natural resonant frequency of movement of a spring element, the method comprising:causing vibratory movement of the spring element;applying an electrical input signal of adjustable frequency and variable phase from a voltage controlled oscillator to a transducer coupled to the spring element;converting movement of the spring element to an electrical output signal;detecting a phase difference between the electrical input signal and the electrical output signal, wherein said phase difference represents an oscillation frequency of the spring element due to accumulation of chemical substances on a surface thereof;integrating the phase difference to provide an input to the voltage controlled oscillator; andwherein the voltage controlled oscillator adjusts the frequency of the electrical input signal until the phase difference which is obtained corresponds to the natural resonant frequency of vibratory movement of the spring element.