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(a)
(b)
Fig. 2. (a) Top-view of the ac
(b) Bottom-view of the acceler
ccelerometer with piezoresistors and metal lines interconnecti
rometer
ions
Tab
ble 1. Accelerometer design parameters
Design parameter
Die size
Beam length( l)
Beam width(w)
Beam thickness(t)
Proofmass size (top) B
Proofmass size (bottom) b
Proofmass height
Piezoresistor size
Dimensions
6 mm × 6 mm
800 µm
150 µm
20 µm
2.8 mm × 2.8 mm
2.362 mm × 2.362 mm
310 µm
70 µm × 10 µm × 0.5 µm
3
Design Calculat
tions
Prior to implementation of
performed using the first ord
the design in COMSOL, analytical design optimization
der equations (1) to (8) given in Table 2, as follows:
n is
Table 2.
. Accelerometer design parameter equations
Parameter
Volume of a single spring
Volume of proofmass
Proofmass
Spring constant (single spring)
Displacement
Maximum stress [5]
Relative resistance change [6]
Voltage output
Formula
Equation no.
V b = l ×w×t µm³
(1)
V pm = 1/3 (B 2 ×H-b 2 ×h)+V s µm³
(2)
M = 2.329×10 -9 ×V pm mg
(3)
K = (E×w×t 3 )/( l 3 ) N/m
[4]
(4)
X = (M ×a )/(4×K) µm
(5)
T = (3×M× a × l )/(4×w×t 2 ) Pa
(6)
ΔR/R = (π l × T l ) + (π t × T t )
(7)
V out = ΔR/R × V in Volt
(8)
 
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