Sketch and describe the operation of a strain-gauge sensor for measuring acceler
ID: 2293160 • Letter: S
Question
Sketch and describe the operation of a strain-gauge sensor for measuring acceleration [5 marks] The above sensor is used to measure the vibration of an engine operating at 6000 rpm. The main component of the signal is sinusoidal with a frequency of 100 Hz and has an amplitude of 2.05 mV. What is the root-mean-square (RMS) noise amplitude if the signal-to-noise ratic (SNR) is 43 dB? [4 marks] Calculate the linear SNR, RMS signal amplitude and RMS noise amplitude after amplification of the signal described in (b) using an amplifier with a gain of 75 and a noise figure of 4dB [4 marks] The signal described in (b) is digitised and displayed on a computer, Figure Q6d below depicts the result. What error has been made and how could it be rectified? [4 marks] 0.5 0.5 0.05 0.15 Time, s 0.2 0.25 0.3 Figure Q6d What is the smallest number of bits that could be used to measure a signal, which varies from 0 V to 5 V, with a resolution of 0.05 V or better? [4 marks] A 10-bit ADC with a reference voltage of 20V outputs a value of 0100101100, what voltage does this represent and what is the range of values that the original analogue voltage could have had? [4 marks]Explanation / Answer
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Please find the answer to the last 2 questions attached as under. Please give a thumbs up rating if you find the answer useful! Have a rocking day ahead!
5. Range = 0 till 5 volts
Resolution = 0.05 volts.
Min number of discrete steps required from ADC = 5/0.05 = 100
For 100 steps, we use a 7 bit ADC, which gives 27 ?steps = 128 steps.
6. Full scale value of the 10 bit ADC = 20 volts
Decimal equivalent of 10 bits = 210 ? = 1024
Decimal equivalent of 0100101100 = 300
1024 decimal gives 20 volts.
Thus, 300 decimal gives (20/1024) x 300 = 5.85 volts.
?Step size = 1/1024 = 0.9 x 10-3
Quantization error = Step size/2 = 0.45 x 10-3
Therefore, range of analugue voltages possible at input = 5.85 +/- 0.45 x 10-3
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