The assessment tier for this course work is Tier 2. Please read the accompanying Gen AI document for this assignment to understand the specification for Gen AI use.  Students  are  expected  to  submit  a  GenAI  declaration  form  with  this assignment.

Task

You are designing an engine control system. One of the control inputs for this system is the vibration level of the engine. You have selected a Measurement Specialties 3028 accelerometer (±10g version). Its datasheet is available on the ELEC6203 course website. You need to design a circuit to interface with it,  amplify  the  signal,  filter  out  unwanted  vibration  frequencies,  and  introduce  as  little  amplitude distortion as possible. It needs to connect to a data acquisition unit with an input impedance of 100Ω . You should assume that you have access to a +5Vpower supply.

You should address the following points, and document them in a report:

1.    What are the  advantages and disadvantages of this type of accelerometer?  What type(s) of interface  circuit would be  suitable  for this  device? What  are the  important parameters to consider?

Break down:

Give a short review of the different categories or types of accelerometers that exist in literature, include enough references besides the lecture notes.

Determine the category to which the 3028 accelerometer you will be using in this work belongs?

Give at least 3 advantages and 3 disadvantages ofthis category over the other types you discovered from the literature.

What interface circuitry is typically required for the type of accelerometer you will be using in this coursework?

When choosing this interface circuit, what are the parameters you will need to consider to ensure you get the best result or performance?

2.    Find  the  (simplified,  ideal)  equivalent  circuit  of  the  accelerometer,  and  simulate  it  at  a reasonable range  of frequencies  and  amplitudes  to verify the behaviour  of its  differential outputs. You are encouraged to do this in NI Multisim. You should set up the simulation so that the input vibration amplitudes and frequencies can be easily varied. You should assume that the resistances are precisely matched, and the sensitivity is in the centre of the range specified in the datasheet.

Break down:

Study the accelerometer datasheet to find out the manufacturer’s recommended equivalent circuit for this accelerometer:   Here   is    the   link    to   the   datasheet:   https://datasheet.octopart.com/3028-010-N- Measurement-Specialties-datasheet-8889413.pdf

What does this equivalent circuit look like?

Replicate this circuit on NI Multisim – (Hint: refer to the lecture 3 on the assignment to see how to simulate this).

Ensure the output of your accelerometer gives the desired voltage output that is typical of the sensitivity range of the accelerometer version ((±10g version) stated in the datasheet.

Check that your simulated model works for different frequencies and amplitudes (i.e. frequency and amplitude voltage values of the voltage controlled resistor)

3.    Connect the outputs from the accelerometer to a differential amplifier, and the amplifier output to  the  100Ω  resistive  load.  You  should  choose  appropriate  components  to  increase  the sensitivity to 100 ±5 mV/g, and explain why you chose this op-amp and the other components. Analyse and document the circuit’s performance.

Break down:

Connect your working equivalent circuit to a differential amplifier; - Listen to lecture 1 to understand what will need to consider when designing your own differential amplifier for this accelerometer.

To design the differential amplifier in Multisim – Go to the component library (see lecture notes on using Multisim) and choose the right op-amps justifying why you chose it (remember you have access to only +5V power supply).

Also justify the reason for the values of other components you will require for designing your differential amplifier.

Once you have completed this, run your model. Ensure it works at different frequency and amplitude values of the voltage controlled resistor and that you have a sensitivity or amplification of 100 ±5 mV/g

Discuss how your choice of components affected the results you obtained from your simulation – Did you achieve the required sensitivity?

If your answer is NO, what did you do to increase your sensitivity to the required value?

If your answer is YES, explain why your design worked.

4.    Evaluate the effect of matching the input impedance of the differential amplifier with the output impedance  of  the  accelerometer  on   system  performance.  You   should  present  this  both theoretically (for an ideal circuit) and with simulation.

Break down:

What happens to the sensor performance when the equivalent resistance ofaccelerometer circuit matches the input resistance of the amplifier; how does this affect the simulated result.

Explain through simulation i.e. simulate a matched circuit and compare result with question 3. What parameter(s) has been affected by this change?

Do the same thing theoretically.

Hint: Figure out a parameter that will most likely be affected and try to calculate the value of this parameter for a matched and unmatched system (read or listen to lecture 1 again for guidance).

5.    Replace the differential amplifier with an instrumentation amplifier (you should construct this from individual op-amps, rather than using a dedicated instrumentation amplifier component). Again,  choose  appropriate  components. Analyse  and  comment  on the performance  of the circuit. How does this performance differ from the differential amplifier?

Break down:

Repeat the procedure in question 3.

Briefly  explain  the  difference  you  observed  (if  any)  in  your  simulated  results  between  using  the differential amplifier and the instrumentation amplifier.

6.    The control system is only interested in vibration in the range 20-170 Hz; you should add an active filter to your circuit so that unwanted frequencies are removed. The priority is to have as little amplitude distortion as possible in the pass-band. You should achieve a roll-off of around

- 40dB/decade. You are expected to explain your design, please do not use automated filter design tools for this. Present tests for the complete system, at a range of input frequencies to confirm that the system performs as designed.

Break down:

Determine what type of active filter is required to achieve the frequency range required? (Read or listen to lecture 2 again)

Read         more          about          filter         design          on          the          recommended         resource:

https://web.mit.edu/6.101/www/reference/op_amps_everyone.pdf

To choose your components, go to the component library in Multisim (see lecture 3 for guidance) Explain the choice of your components for your filter design.

Connect your filter to the output of your instrumentation amplifier and run the simulation

Check the output of your simulated filter at different frequencies and amplitude of the accelerometer - Did you achieve the required frequency range, sensitivity and roll-off?

If your answer is NO - Check your filter design again. Confirm you have chosen the right filter and try a range of different op-amps in the component library and adjust the values of other components.

If your answer is YES - explain why your design works.

Make sure you present the complete circuit in your report (equivalent accelerometer + instrumentation amplifier + filter) all connected and functional.

7.    Evaluate  the  overall  current  draw  of the  system.  Improve  this,  but  maintain  the  required sensitivity. What did you change? How has it affected performance?

Break down:

Check the amount of current drawn by your filter, instrumentation/differential amplifier and equivalent circuit designs using the “current probe” in Multisim.

Determine at least 2 things you can do to reduce the total current draw in your complete circuit (listen to lecture 2)

Simulate  and  explain how this change you have made in your or component  affects the  expected performance of the circuit?

Submission and Feedback

Your document should be formatted as a single-column technical report. You should record your work concisely and include references. Minimum point size 11, maximum of 15 pages.

Break down:

Make sure your report has an Abstract. Follow a typical IEEE single column template.

Ensure you discuss your results i.e. give explanation as to why your result is what they are.

Provide a conclusion, summarising the key concepts what you have discovered or learnt through this coursework regarding designing interface circuits for sensors.