Brands
Vishay Measurements Group
Interactive Guide
Tech Notes
TN-510
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Design Considerations For
Diaphragm Pressure Transducers
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NUMERICAL EXAMPLE
U.S. Customary and Metric (SI) Units Assume that a diaphragm pressure transducer is to be designed for a maximum rated pressure of 1000psi ( 6.89 MPa) , under which pressure the output ( 
) from a steel diaphragm should be 2 mV/V. If the
diaphragm diameter is to be 0.670 in (
17.02 mm
), find the following:
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Diaphragm Thickness
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U.S. Customary
P
=
1000
lbs/in
2
=
0.283
lbs/in
3
E
=
30
x
10
6
psi
g
=
386.4
in/sec
2
=
0.335
in
=
2
mV/V =
2
x
10 -3 V/V
v
=
0.285
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From Eq. (4), solve for
t
,
with
in units of V/V
t = 0.036 in |
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CONSTANTS*
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Metric (SI)
P
=
6.89
MPa
=
8.51
x
10
-3
m
v
=
0.285
=
2
mV/V
=
2
x
10 -3 V/V
E
=
207
GPa
p
=
7.83
g/cm
3
=
7.83
x 10
3
kg/m
3
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t = 9.11 x 10 -4 m = 0.911 mm |
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Center Deflection
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U.S. Customary
P
=
1000
lbs/in
2
=
0.283
lbs/in
3
E
=
30
x
10
6
psi
g
=
386.4
in/sec
2
=
0.335
in
=
2
mV/V =
2
x
10 -3 V/V
v
=
0.285
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From Eq.(5),
=
0.0016
in
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CONSTANTS*
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Metric (SI)
P
=
6.89
MPa
=
8.51
x
10
-3
m
v
=
0.285
=
2
mV/V
=
2
x
10 -3 V/V
E
=
207
GPa
p
=
7.83
g/cm
3
=
7.83
x 10
3
kg/m
3
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= 3.98 x 10
-5
m
=
0.0398
mm
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Resonant Frequency
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U.S. Customary
P
=
1000
lbs/in
2
=
0.283
lbs/in
3
E
=
30
x
10
6
psi
g
=
386.4
in/sec
2
=
0.335
in
=
2
mV/V =
2
x
10 -3 V/V
v
=
0.285
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From Eq.
(6),
= 31 766 Hz
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CONSTANTS*
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Metric (SI)
P
=
6.89
MPa
=
8.51
x
10
-3
m
v
=
0.285
=
2
mV/V
=
2
x
10 -3 V/V
E
=
207
GPa
p
=
7.83
g/cm
3
=
7.83
x 10
3
kg/m
3
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From Eq.
(7),
= 31 647 Hz
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Approximate Maximum Diaphragm
Strain Level |
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U.S. Customary
P
=
1000
lbs/in
2
=
0.283
lbs/in
3
E
=
30
x
10
6
psi
g
=
386.4
in/sec
2
=
0.335
in
=
2
mV/V =
2
x
10 -3 V/V
v
=
0.285
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(d) From Eq. (2),
= -1989
in/in
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CONSTANTS*
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Metric (SI)
P
=
6.89
MPa
=
8.51
x
10
-3
m
v
=
0.285
=
2
mV/V
=
2
x
10 -3 V/V
E
=
207
GPa
p
=
7.83
g/cm
3
=
7.83
x 10
3
kg/m
3
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= -2001
m/m
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* The small differences occurring in comparable U.S.
Customary and Metric results arise from rounding numbers
in both sets of calculations.
Page 12 of 12