## Post Lab 7 Answer Sheet

### Lab Members

Be sure to use a standard demo sheet for the lab demonstrations.

### Quantization Questions

Submit the results of your quantization measurements.

Voltage
Range (mv) |
Conversion
Value |

0
<---> |
0 |

<---> |
0<-->1
unstable |

<---> |
1 |

<---> |
1<-->2
unstable |

<---> |
2 |

<---> |
2<-->3
unstable |

<---> |
3 |

<---> |
3<-->4
unstable |

1) What is the voltage range for the first conversion interval (0)?
How might this voltage range have come about (hint: think binary...)

2) What is the voltage range for the subsequent intervals?
How might this voltage range have come about (hint: think binary...)

3) What transfer function graph illustrated in the In-Lab does this
ADC represent?

4) Is there any advantage generally speaking to this transfer
function compared to the other? (Hint: Consider how the quantizing
error is expressed.)

### Sampling Questions

1) At what frequency did you notice the aliasing frequency was
nearly zero? How does it compare to the sampling frequency?

2) At what frequency did you notice the reproduced freq was half
the
sampling frequency? Does this follow the aliasing prediction?

3) At what frequency did you begin to notice quantizing steps in the
reproduced signal? In light of the sample frequency, why does this
become easy to observe?

4) For the on 1KHz source frequency example, how many quantizing
steps did you observer per cycle? What is the ratio of the source
frequency to the sampling frequency? How does this compare to the
number of quantizing steps you observe?

5) The amplitude of the low pass signal was considerably lower than
expected for the 3db down frequency. This is from the DAC source
resistance output loading the filter and effectively changing the 3b
down point frequency. After adjusting the source frequency, at what
freq did you find the 3db point to be?

6) Given the RC values of the
filter and the measured 3db freq, what value do you think the DAC
source resistance is? Hint: The combined filter resistance is the DAC
source
resistance plus the filter resistance. Check the SmartFusion
specification and see how the DAC source
resistance compares to your calculated value. Smartfusion
Data Sheet
Hint: Search for DAC output impedance.

### Accelerometer Questions

1) What voltage values did you
measure for the 3 orientations of
the
accelerometer Y axis? How many volts per G do you observe? Is this
consistent with the specification?

2) Show your calculations for determining Raccel. Do these compare with
the accelerometer specification. Freescale
MMA7361L