High Precision Acceleration Sensor

High Precision Acceleration Sensor
1. General Description
A new bulk micro machined multi-use
acceleration sensor has been developed. The
sensor could provide a measurement range of
±8g, a resolution of 500µg at 200Hz bandwidth
and a bias stability better than 100mg. A
differential capacitor design based on bulk
micro machined and wafer bonded elements is
chosen for the sensor because this approach
supplies a large inertial mass in combination
with small capacitor gaps. So the sensor can
reach a high sensitivity. The differential
capacitor arrangement can be used both for
detection of small deflections of the movable
mass and for force compensation using
electrostatic forces. The closed-loop operation
principle enables a high resolution.
The acceleration sensor was developed and
built up in cooperation with Gemac mbH
Chemnitz.
Fig. 2: SEM picture of the spring-mass system
2. Features
•
•
•
•
Differential capacitor design in closed-loop
operation
Bonded glass plates include fixed
electrodes
Seismic mass suspended by vertical
torsional beams
High sensitivity, high resolution and high
bias stability
3. Suggested applications
•
•
•
Airborne navigation and positioning
Automotive applications
Acceleration measurement
Fig. 3: Ground plate with mounted inner box and electronics
4. Characteristics
Parameter
Measurement range:
Resolution:
Bandwidth:
Bias stability:
Torsional resonant
frequency:
Shock resistance:
Spring width:
Chip size:
Value
+8
500
200
>100
400
Unit
g
µg
Hz
mg
Hz
80 / 5
16
7 x 7 x 1.7
g/ms
µm
mm³
5. Contact
Fig. 1: Schematic cross section
Ralf Schmiedel
Phone: +49 (0) 371/531-33253
Fax:
+49 (0) 371/531-24069
E-Mail: ralf.schmiedel@enas.fraunhofer.de