Question

1. Calculate the step values for the following ADC bit sizes over a range of 0 to 3.3v.

a.4 Bit b.8 Bit c.10 Bit d.12 Bit

2.Calculate the step size for 4, 8, 10, and 12 Bit analog to digital conversation of the temperature sensor with a range of 90 to 100 degrees fahrenheit.

3.Identify the minimum ADC bit size that is needed to convert the temperature with one tenth of a degree accuracy.

Answer 1

Ans 1) The step value for ADC over a range of voltage is given as  

where Vr is the reference voltage given and n is the number of bits.

So, Step value =     --------------------------------------> ( eq 1)

a. 4 Bit

We have Vr=3.3 V and number of bits is 4 thus n=4.

Substituting these values in eq1,

=>Stepsize = 3.3 / 2⁴ V

=>Stepsize = 3.3 / 16 V

=>Stepsize = 0.2063 V

b.8 Bit

We have Vr=3.3 V and number of bits is 8 thus n=8.

Substituting these values in eq1,

=>Stepsize = 3.3 / 2⁸ V

=>Stepsize = 3.3 / 256 V

=>Stepsize = 0.0128 V

c.10 Bit

We have Vr=3.3 V and number of bits is 10 thus n=10.

Substituting these values in eq1,

=>Stepsize = 3.3 / 2¹⁰ V

=>Stepsize = 3.3 / 1024 V

=>Stepsize = 0.0032V

d.12 Bit

We have Vr=3.3 V and number of bits is 12 thus n=12

Substituting these values in eq1,

=>Stepsize = 3.3 / 2¹² V

=>Stepsize = 3.3 / 4096 V

=>Stepsize = 0.0008V