GeoSIG AC-4x-DH Accelerometer

The AC-4x-DH sensor package, now a legacy product, was a triaxial accelerometer designed for borehole applications regarding strong motion earthquake survey and monitoring. The AC-4x accelerometer was based on the modern MEMS (Micro Electro-Mechanical Systems) technology, consisting of sensing cells assembled in a way that optimises their performances. This combined with the state of the art proprietary circuit design yielded this cost effective and reliable accelerometer.

MEMS cells include linear accelerometer sensing elements which measured the capacitance variation in response to any movement or inclination and a factory trimmed interface chip that converted the capacitance variations into analog or digital signal proportional to the motion. The DC response allowed the sensor to be easily repaired, tilt tested or recalibrated in the field. With the help of the TEST LINE the AC-4x accelerometer could be completely tested assuring proper operation.

The downhole casing contained the entire sensor system. The sensor was connected through Overvoltage Protection stage to the recorder at the surface with a cable.
Using inclinometer tubes and the provided guiding wheels, the sensor could be oriented before insertion in the tube.

General Characteristics
Application
Strong Motion earthquake recording Vibration monitoring Alarm / Switch Systems

Configurations:	Triaxial	Biaxial	Uniaxial	Axes	Alignment**
AC-43	X			X – Y – Z	H – H – V
AC-42-H		X		X – Y	H – H
AC-42-HV		X		X (or Y) – Z	H – V
AC-41-H			X	X (or Y)	H
AC-41-V			X	Z	V

* i : Internal sensor ** H: Horizontal, V: Vertical
Full Scale Range:
± 2G std, optional ± 0.625, ± 1, ± 4 or ± 5G
Sensor Element
Sensor Element Type:
MEMS Inertial Sensor
Dynamic Range:
> 88.5 DB at 2G FS (0.1 to 30Hz), 96.5 DB at 5G FS
Noise:
50 ugRMS
Nonlinearity:
<0.3% typ, <0.6% for vertical
Cross Axis Sensitivity:
<2%typ
Bandwidth:
DC to 100Hz
Span Drift:
100 ppm/°C
Offset Drift
± 0.8 mg / °C
Full Scale output:
0 ±10 V differential (20 Vpp)optional 2.5 ± 2.5 V single-end (5 Vpp)0 to 20 mA current loop
Measuring Range
See Plot
Power
Supply Voltage:
7 to 15 VDC, single supply, optional, 7 to 30 VDC
Consumption:
9 mA @12 VDC
Connector:
Metallic, Shielded, IP67, 12 pins, male. optional MIL, Bendix PT07A 14-19P.
Mating:
Binder / Coninvers type RC
Overvoltage Protection:
All pins are protected
Connector Pin Configuration
Pin 1-6:
Signal output for axis X, Y, Z
Pin 7-8:
Test input
Pin 9-10:
+12 VDC Power Supply
Pin 11-12:
not used)
Case:
Shielded Ground
Environment/Housing
Housing Type:
Aluminium cylinder, fully sealed
Housing Size:
Diameter 55 mm, length 420 mm
Weight:
3.5 kg
Index of Protection:
IP 68, up to 10 bars water pressure
Temperature Range:
- 40 to 85 °C (operating)
- 40 to 85 °C (non-operating)
Humidity:
0 to 100 %
Orientation:
Using 3” inclinometer casing (Figure 1) with included guidewheels (Figure 2).
Standard AC-43-DH
Full scale ± 2 g, Sensor mating connector and user manual
Optional Accessories
DH-TUBE:
3” inclinometer casing as in figure 1 in sections of 3 meters with coupling elements.
Installation kit:
All required tools and fixation consumables for up to 100 meters of casing.
DH-Ball
Glass Balls for settlement of downhole sensor (25 kg bag)
Ordering Information
Specify:
Type of AC-4x-DH, acceleration full scale, depth of borehole and total cable length.
**Specifications subject to change without notice