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Sensor Signal Acquisition and Processing Laboratory Project module 3 Instructions: Perform all the tasks in this laboratory project

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Sensor Signal Acquisition and Processing Laboratory Project module 3

Instructions: Perform all the tasks in this laboratory project. Each student is to write an individual report containing all your results, observations and comments. Submit 2 files through Stream by the due date:

1. Your report, in Word or PDF format.

2. A compressed file (ZIP file) containing your Matlab and Simulink code.

Your Matlab code should be functioning and easy to read, with appropriate comments. I should be able to run your code and obtain the results in your report without having to make changes to any source code.

This project consists of two parts. The first part should be completed during the laboratory hours where some supervision is provided. The second part is to be completed on your own using the knowledge gained from the lectures.

Plagiarising results, any part of your report, or Matlab code will be severely penalised.

Late submissions will be penalised by 10% deduction of marks per day up to a maximum of 5 days, after which submission will not be marked. Requests for extension must be made before the due date. They will only be granted under exceptional circumstances.

Part 1

1) Load cell modelling:

Given the above waveform of the load cell impulse response, estimate the resonant frequency

and decay rate.

Verify your results by using your estimated pole locations to plot the impulse response.

Given that the unloaded load cell (including weighing platform) has an effective mass of 125 g, calculate the spring constant and damping factor for the load cell.

The load cell has a full scale load of 1000 g. Calculate the new pole and zero locations for the

fully loaded load cell. Why are they different?

Plot the impulse response of the fully loaded load cell. Is the weight easier or harder to measure when the load cell is fully loaded? Explain your answer.

Choose an appropriate cut frequency for the load cell amplifier so that your system will handle any load from 0 to 1000g.

Calculate the coefficients of the numerator and denominator of your load cell and amplifier system at both no-load and full-load. Use these to plot the frequency responses of the system at no-load and full-load (on the same graph).

Plot the response of the system to adding a full load when there is no load (step response).

Plot the response of the system to removing the full load (negative step response).

2) A/D Conversion:

From looking at the waveforms, do you need a unipolar or bipolar A/D convertor?

What is the minimum sample rate required to capture this signal?

Given that the full scale load cell output (ie 1000g load, after settling) is 5mV, choose your

amplifier gain such that the signal is between 0 V and 1 V for unipolar, or between -1 V and 1 V

for bipolar.

How many bits are required to achieve an accuracy of ±0.5 g?

If you only have available a 10-bit A/D converter, calculate the minimum sample rate to achieve

the required accuracy after down-sampling.

3) Multi-rate processing:

A signal is in the range of 0 to 500 Hz. A multi-rate system is used to reduce the sample rate of from 20 kHz to 1.5 kHz. The system should introduce an error of no more than 0.1% of full scale.

Derive the filter specifications for the filter associated with this system? What order of filter is required?

If the noise spectrum is flat, calculate the improvement in signal to noise ratio as a result of changing the sample rate.