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Jun11-10, 02:41 AM
1. The problem statement, all variables and given/known data
This is a practice exam problem and im getting an answer i feel is definately not right. Anyways here is the question...
You are designing a system to measure the magnetic field generated by an
electromagnet. This forms part of a feedback control system to keep the magnetic
field constant during an experiment. The system must provide an output voltage in the
range 0 to 5 volts, such that 5 volts corresponds to a magnetic field intensity of 1
Tesla. You have a n-type silicon-based Hall Effect sensor with the following
Dimensions: 10 mm long x 5 mm wide x 1 mm thick
Electron concentration: 1 x 1017 cm-3
Resistivity: 0.1 W-cm
Excitation current: 10 mA
a) Explain the principle of the Hall effect.
b) Determine the output voltage of the Hall sensor for B = 1 Tesla.
c) Sketch a diagram of your proposed measurement circuit. Explain the operation of
the circuit and your reasons for choosing various components.
d) Determine the values of any component values, amplifier gains, etc required in
your circuit. Show you analysis.
e) Determine an explicit expression for the transfer characteristic of your magnetic
2. Relevant equations
Im stuck at part b)
Ive been trying to use the formula Vh = (IB)/(q.n.t)
Vh = Hall voltage
I = current, which is 10x10-3 A
B = magnetic field, which is 1 T
q = charge, which is 1.602x10-19 C
n = number of charge carriers, which is 1x1011 m3
t =thickness, which is 1x10-3 m
3. The attempt at a solution
Using the above formula an converting the variables i obtain an answer of 624x106 V, which is obviously not correct.
Any help with part b would be greatly appreciated.
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