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| Circuit Diagram |
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1. Electric charge converter
2. Amplifier
3. Lowpass filter
4. Smith trigger
5. Stabilized voltage supply
6. Output amplifier
7. Power supply |
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1. Electric charge converter
2. Amplifier
3. Lowpass filter
4. Smith trigger
5. F/V converter
6. Stabilized voltage supply
7. V/I converter
8. Power supply
9. Load resistor |
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Electric charge converter
Convert the alternating charge from piezoelectric unit into voltage, which is proportional to quantity of the charge.
Alternating amplifier and low-pass filter
Amplify signal and eliminate noise. When the velocity is low, high frequency noise produced from pipe vibration may be superposed on the output wave of charge converter to form a superposed wave. When high velocity, differential pulsed signal forms a wave involved low frequency swing. At low velocity (small output voltage), high frequency noise be eliminated by lowpass filter, and at high velocity (large output voltage), along with the lowpass feature be released and its feature of amplitude limit to appear, to prevent the signal from amplifying low frequency noise.
Smith trigger
Convert the detected voltage of the vortices frequency into pulse signal with a range of amplitude. Due to circuit of Smith trigger has a hysteretic function to input and output signal, therefore it can prevent oscillating caused by noises.
F/V converter
Convert pulse signal from Smith trigger output into analog vlotage that is proportional to frequency.
V/I converter
Convert analog output voltage into 4~20mA DC.
Pulse output amplifier
Amplify pulse frequency signal from Smith trigger. |
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