| 摘要 |
PURPOSE:To make it possible to stably measure conductivity up to a lower degree, by forming a resonance circuit by connecting a condenser to a detection coil and performing the positive feedback of the resonant voltage thereof to draw the frequency of an oscillator in resonance frequency. CONSTITUTION:An electromagnetic induction current is flowed to a water loop by exciting a magnetic core W1 by the output of an oscillator to induce electromotive force in a detection coil L2. A condenser C5 is connected to the coil L2 to form a resonance circuit and the resonant voltage thereof is supplied to a DC ammeter A through an amplifier Q1 and a detector D1. In this case, the output voltage of the amplifier Q1 is positively fed back to the oscillator through an amplifier Q2 and the oscillation frequency of the oscillator is dawn in the frequency of the resonance circuit consisting of L2 and C5 to eliminate the difference between both frequencies. Therefore, detection can be performed always in a stable state with high sensitivity.
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