PROBLEM 12.1
KNOWN:
A linear potentiometer having
D
= 0.1 mm
ρ
e
= 1.7
×
10
-8
Ω
-m
R
= 1 k
Ω
FIND:
a) for a core diameter of 1.5 cm, determine the range
b) plot loading error as a function of displacement
SOLUTION:
a) In order to determine the number of turns of wire, N
R
L
A
L
RA
e
c
c
e
=
⇒
=
ρ
ρ
with
A
c
=
×
=
×
−
−
π
4
0 1
10
7 854
10
3
2
9
.
.
m
m
2
c
h
yields
L
=
×
×
=
−
−
1000
7 854
10
1 7
10
462
9
8
m
- m
m
2
Ω
Ω
b
gc
h
.
.
One turn takes
π
(1.5) cm of wire, thus
N
=
×
=
462
9804
m
1.5
10
m
-2
π
c
h
Then since each turn occupies approximately D = 0.1 mm the range is
(9804)(0.1 mm) = 0.98 m

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