The AC-23-DH sensor package, now a legacy product, was a triaxial accelerometer designed for borehole applications regarding Strong Motion earthquake survey and monitoring. The AC-2x-DH sensors were servo-accelerometers based on a standard exploration geophone mass-spring system with electronic feedback. This type of sensor gives a very good stability versus temperature or aging because of the very simple principle. The sensor did not require maintenance and had very low aging drift. With the help of the TEST LINE the sensor could be easily, completely tested.

The family of AC-2x-DH accelerometer was directly compatible with the GeoSIG recorders. 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 survey industrial applications requiring high sensitivity
•  

  Configurations:	Triaxial	Biaxial	Uniaxial	Axes	Alignment**
  AC-23	X			X – Y – Z	H – H – V
  AC-22-H		X		X – Y	H – H
  AC-22-HV		X		X (or Y) – Z	H – V
  AC-21-H			X	X (or Y)	H
  AC-21-V			X	Z	V

• ** H: Horizontal, V: Vertical
• Full Scale Range:
• Factory configurable to: ± 0.1, ± 0.2, ± 0.5, ± 1, ± 2 and ± 4g for ± 10 V diff at output AC-23 NPP: ± 0.5, ± 1 and ± 2g

• Sensor Element

• Type:
• Servo-accelerometer based on geophones with feedback
• Dynamic Range:
• >125 dB effective at ± 2 g full scale
• Linearity:
• 0.1%
• Accuracy:
• ± 0.4 dB max over the bandwidth
• Cross Axis Sensitivity:
• 1%
• Bandwidth:
• 0.1 Hz (1 pole) to 100 Hz (1 pole)optional 200 Hz
• Damping:
• 0.7 critical
• Offset Drift
• < 1 mV/0C
• Span drift:
• < 200 ppm/0C
• Full Scale output:
• 0 ± 10 V differential (20 Vpp)
• Measuring Range
• See Plot
• 

• Interface

• Power supply voltage:
• 12 VDC regulated (10 to 15 V)
• Consumption:
• 40 mA @ 12 V
• Connector:
• Metallic, Shielded, IP67, 12 pins, male mounted at end of cable.Other connectors on request.
• Mating:
• Binder / Coninvers type RC
• Overvoltage Protection:
• All pins are protected

• Connector Pin Configuration

• Pin 1-2, 3-4, 5-6:
• Signal output for axis X, Y, Z
• Pin 7-8:
• Test input, Digital test-pulse (0 / 12 V)
• Pin 9-10:
• +12 VDC Power Supply
• Pin 11-12:
• Auxiliary input (unused)
• Case:
• Shielded Ground

• Environment/Housing

• Housing Type:
• Aluminium cylinder, fully sealed
• Housing Size:
• Diameter 54 mm, length 420 mm
• Weight:
• 3.5 kg
• 
• Index of Protection:
• IP 68, up to 10 bars water pressure
• Temperature Range:
• - 20 to 70 °C (operating)
  - 40 to 90 °C (non-operating)
• Humidity:
• 0 to 100 %
• Orientation:
• Using 3” inclinometer casing (Figure 1) with included guidewheels (Figure 2).
• Standard AC-23 DH/DH Ball
• Full scale ± 2 g, recorder mating connector and user manual on CD. Borehole cable length to be defined.

• 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-2x-DH, acceleration full scale, depth of borehole and total cable length.
•  
• 

• **Specifications subject to change without notice

• Full Scale    ± 0.1, 0.2, 0.5, 1, 2 and 4g jumper selectable
• Bandwidth 0.1 Hz to 100 Hz (optional 200 Hz)
• Dynamic range > 125 dB
• Excellent temperature stability
• Strong-Motion, Free field and Industrial applications
• No field adjustment required
• Strong mechanical design
• Fits in 3 inch casing