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AC-23 Accelerometer User Manual
11.08.2022 / V17
The surface should have a scribed north/south orientation line accurately surveyed from reliable markers. The
X-axis of the sensor must be pointed to East or to any other main direction of the structure to monitor.
One M8 expanding nut rock anchor must be used for the sensor fixation.
4 Theory of operation
4.1 Introduction
The AC-23 sensor package is a triaxial accelerometer designed for free field and industrial applications
regarding STRONG-MOTION earthquake survey, monitoring and research. This sensor is well suited for
applications where a high sensitivity is required.
The AC-23 sensor can be optionally installed into a rugged protective housing. This optional protective housing
is in stainless steel for optimal environmental resistance. As option, the protective housing could be executed
with an IP68 grade for free field location where the possibility exists of housing submersion.
The sensor could be installed on floor or wall with a modification of the axis organization. With the help of the
TEST LINE, the complete sensor can be very easily completely tested. Full scale can be field selected by the
user with jumpers.
4.2 Principle
The accelerometer is based on a geophone mass-spring system with electronic correction. This type of
sensors gives a very good stability in temperature and aging because of the very simple principle. It uses a
damped mass spring oscillator called "Geophone" to convert seismic movement into electrical value
proportional to the velocity. In a graphic with constant acceleration, the geophone response will present a
maximum at the frequency called "Natural Frequency" which is the resonant frequency of the mass-spring
oscillator. Above and below this point, the response will decay with one pole slope (±20 dB / decade). The
corrector will over-damp the geophone by applying a voltage with opposite polarity over the geophone and the
output response will be flat and proportional to the acceleration in this frequency band.
Motion on
geophone
the X axis
4.5 Hz
Motion on
geophone
the Y axis
4.5 Hz
Motion on
geophone
the Z axis
4.5 Hz
Note : all inputs, outputs & power supply entry are surge protected.
Pulse
scaling
Low pass
Feedback
amplifier
filter
Feedback
Low pass
amplifier
filter
Low pass
Feedback
amplifier
filter
Figure 4 AC-23 Sensor block diagram
Test input
Differential
Output
Output to
amplifier
recorder
Differential
Output
Output to
amplifier
recorder
Differential
Output
Output to
amplifier
recorder
+8 V
Power
- 8 V
supply
9/15 Vdc
7 / 15
GS_AC-23_UserManual_V17
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