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Peak Voltage detection

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dsanthosh67

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Hi all,

Actually i am working with an application to read the Exact Piezoelectric sensor output peak voltage. I tried with some reference design from the internet but i am not able to match the exact voltage between what i read in the adc and the output of piezoelectric sensor(input).kindly guide me solve the issue with some circuit design..

Thanks in advance,
santhoshkumar
 

Audioguru

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The datasheet of the LM3915 bar graph IC shows a few excellent peak detector circuits. The opamps need a dual polarity supply.

In my Sound Level Indicator project I used an opamp that works with its inputs at 0V so it does not need a negative supply. It is inverting so when its input is negative then its output goes positive. A transistor emitter-follower is used as a high speed power rectifier to quickly charge the capacitor and its base-emitter voltage is cancelled by the high open-plop gain of the opamp.
 

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chuckey

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As I understand it you have a transducer that feeds a peak detector which in turn feeds an ADC. So you have measured the output from the peak detector and it does not match the "digital" number from the output of your ADC. So adjust the gain of the ADC until it does.
Or, you are expecting a certain peak output from your transducer (read from the spec. sheet ?) and your ADC's output does not match your expectations and you suspect the peak detector.
As a first stab does your peak detector store the voltage long enough for the ADC to make a valid measurement? i.e. does your ADC always read low? Increasing the pulse repetition rate would lead to higher readings.
Frank
 

acannell

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What is the output impedance of the piezo transducer? Your detection circuit is probably loading it and dropping the voltage you measure. Can you post a schematic of the circuit you are working on?
 

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