Programmable Charge Amplifier

Piezoelectric accelerometer, when subjected to vibration converts mechanical energy into  electrical energy but with very low voltage,  typically in milli-volts. The small level of charge at the output of sensors is not enough for further processing .We use Charge amplifier, which i

Project Title

Programmable Charge Amplifier

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

Piezoelectric accelerometer, when subjected to vibration converts mechanical energy into  electrical energy but with very low voltage,  typically in milli-volts.

The small level of charge at the output of sensors is not enough for further processing .We use Charge amplifier, which is a device that amplifies signal from milli-volt into volts.Input range of amplifier will be up to 100pc(pico coulomb) with sensitivity of 100mv/pc having selectable gain and filter.

A charge amplifier uses an operational amplifier input stage. The configuration of the operational amplifier with the capacitor in the feedback loop operates as an integration network and integrates the current at the input. This input current is the result of the charge developed across the high impedance piezoelectric elements inside the accelerometer. The amplifier works to nullify this current and in doing so produces an output voltage proportional to the charge.

 A single axis piezoelectric accelerometer sensitive along its Z axis conventionally use full over a range of 2Hz up to about   of its mechanical resonance frequency of 15 to 21 kHz depending on its mounted configuration . The charge available on its output is proportional to acceleration sensed by the device (including gravity). To be useful this charge must be inte grated by a charge amplifier to provide a voltage proportional to acceleration. The overall low frequency performance depends on the limiting noise floor and frequency response of the charge amplifier A charge amplifier was designed specially for extending the useful low end of the frequency range of the 20HZ to 2KHz  and to provide antialias Filtering for adequately suppressing frequencies at the mechanical resonance of the accelerometer This filter is a 2nd order active low pass  with zeros in the stop band to cancel the mechanical resonance It provides a flat frequency response to its upper 3 dB cutoff frequency at 6.8 kHz and guarantees at least 20 dB anti alias suppression of all acceleration stimuli above 11 kHz. The charge amplifer should be set for the desired gain and low frequency cutoff .A software interface connected with hardware is to be implemented for selection of gain and filter. The output voltage range of the Charge Amplifier is nominally up to [±10] V.

Project Objectives

      After studying the recent research  and motivated by the problem in existing systems, we are proposing a solution whose objectives are :

To,

• Design a charge amplifier circuit suitable for a piezoelectric accelerometer.
• Interface LCD and keypad with Arduino.
• Adjust the gain and desired frequency of the charge amplifier by using Arduino.
• Adjust the sensitivity of the charge amplifier.(200 mV/pc).
• Design a circuit that is compatible with existing sensors and commercial amplifiers.

Project Implementation Method

The project mainly have two parts. The first one is the integrator which will conert the charge output of the Piezo elctric accelerometer sensor to vlotage and increase its amplitude to a level of 1 volt, that can be used for further analysis. The second part is programmable part which include channel selection, gain slection and filter selection. Basically we need 8 different channel of the output working in parallel, so first we have to select the channel we want to alter using keypad, if we press 1 that means we want to change the output of channel 1 and so on. Once the channel has been selected we need moniter the status of the four swithes through which we will control the gain and filter of the selected channel. Two of the switches control the gain which means can select four different gains and two of the switches controls filter so we can select four different filters frequency. Parallaly the parameters should be displayed on LCD. 

The flowchart in the figure below shows a complete structure of the programmable part.

Benefits of the Project

• The available charge amplifier are too costly, so the main benefit is low cost and easy availability.
• The proposed system have simple structure so its maintenance will be easy.
• It will help the power generation industry in measuring the vibration in heavy machinaries.
• This will help local industry as they are not manufacturing but using it.
• This system can be used for measuring the earthquake.

Technical Details of Final Deliverable

• Piezo electric accelerometer is sesnsor which senses vibration of system in terms of charge.
• An integrator circuit is used to convert the charge output to voltage and amplify it to a level that can be used for further analysis.
• This syste provides different gain selection that can be controlled according to our application.
• The output normally have high frequency components that can removed by using low pass filter.
• We can select different cutoff frequency for the filter according to our need and accuracy we want in the measurement.
• The selected filter and gain is dispalyed on LCD for better user interface.
• 8-channels are devoloped that will work in parallel, to be used for different application.

Final Deliverable of the Project

Hardware System

Core Industry

Manufacturing

Other Industries

Core Technology

Others

Other Technologies

Sustainable Development Goals

Industry, Innovation and Infrastructure, Sustainable Cities and Communities

Required Resources

If you need this project, please contact me on contact@adikhanofficial.com