Sensing instrument

• US 8,051,714 B2
• Filed: 09/27/2007
• Issued: 11/08/2011
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: Nihon Dempa Kogyo Company Limited
• Original Assignee: Nihon Dempa Kogyo Company Limited
• Inventors: Onishi, Naoki, Kukita, Hiroyuki, Wakamatsu, Shunichi
• Primary Examiner(s): SAINT SURIN, JACQUES M
• Application Number:
  US12/311,262
• Publication Number:
  US 20090308142A1
• Time in Patent Office: 1,503 Days
• Field of Search: 735/79, 73/73, 738/611.8, 310/323.21
• US Class Current: 73/579
• CPC Class Codes: G01N 2291/0256 Adsorption, desorption, surface mass change, e.g. on biosensors
• CPC Class Codes: G01N 29/022 Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices microdevices per se B81B
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 5/02 by absorbing or adsorbing components of a material and determining change of weight of the adsorbent, e.g. determining moisture content absorption bulbs B01D53/00
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844

Abstract

In a sensing instrument using a quartz sensor on whose front surface an adsorption layer for adsorbing a substance to be sensed is formed and which changes in natural frequency by the adsorption of the substance to be sensed, the present invention has an object to quickly detect a trouble of the quartz sensor to prevent an operator from recognizing an incorrect measurement result. In the present invention, a level detecting circuit detecting a signal level of an oscillation output of an oscillator circuit is provided, and after the time for stabilization passes after the power-on time, a computer takes a level detection value therein to compare the signal level and a threshold value. Then, when the signal level is lower than the threshold value, the signal level is determined as abnormal and, for example, the abnormality notification is displayed on a display unit, whereby an operator is notified of the occurrence of the abnormality.

Claims

1. A sensing instrument which uses a sensing sensor including a piezoelectric resonator changing in natural frequency by the adsorption of a sample and which senses the adsorption of the sample based on the change in the natural frequency of the piezoelectric resonator, the instrument comprising:

an oscillator circuit oscillating the piezoelectric resonator;

a measuring unit measuring a signal regarding a frequency of an oscillation output of the oscillator circuit;

a level detecting circuit detecting a signal level of the oscillation output of the oscillator circuit;

a level determinator determining that the signal level is normal when the signal level detected by the level detecting circuit is equal to or higher than a threshold value, and determining that the signal level is abnormal when the signal level is lower than the threshold value; and

a notifier notifying that the signal level is abnormal when the signal level is determined as abnormal by the level determinator.

2. The sensing instrument according to claim 1, wherein the piezoelectric resonator includes:

an electrode provided on a front surface of a piezoelectric piece; and

an adsorption layer formed on a front surface of the electrode to adsorb a substance to be sensed, and changes in the natural frequency when the substance to be sensed is adsorbed.

3. The sensing instrument according to claim 1, wherein a timing at which the level determinator makes the determination on the signal level is after a preset time for stabilization passes after power is supplied to the sensing instrument.