DEVICE FOR DETECTING Q OF QUARTZ RESONATOR

• Main Authors: TANABE MASARU, YAMAGUCHI MASATSUNE, HASHIMOTO KIYONARI
• Format: Patent
• Language: English
• Published: 22.07.1997
• Edition: 6
• Subjects: MEASURING; MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES; PHYSICS; TESTING

PROBLEM TO BE SOLVED: To continuously measure the Q of a quartz resonator by giving frequency- controllable input signals to a bridge circuit containing the quartz resonator and controlling the frequency of the input signals by using a phase difference signal between the differentially converted output signal of the bridge circuit and the input signals, and then, adjusting the output to a peak. SOLUTION: AC signals are inputted across the diagonal inputs (a) and (b) of a bridge circuit 10 from a voltage-controlled oscillator 16 through an automatic gain adjusting circuit 17 and the AC outputs across the inputs (a) and (b) corresponding to the Q of a quartz resonator are converted into a differential signal by means of a differential amplifier 12. The differential signal is inputted to a phase comparator 14 together with the input signal of the circuit through a phase correcting circuit 13 and the comparator 14 outputs the phase difference signal between both signals. The phase difference signal is converted into a DC voltage through an LPF 15 which is adjusted so that the response characteristic of a PLL circuit can become the optimum and a phase locked loop is formed as the control voltage of the oscillator 16. Therefore, the output of the amplifier 12 always becomes proportional to the maximum conductance at the resonance point of the resonator and an output voltage to be found is obtained by passing the output through a detector 20, a rectifier 21, and a capacitor 22.