The Post-hole Digital Alpha-TADP120-Light is a three component low noise feedback, DIGITAL OUTPUT velocity broadband seismometer designed to be installed in post-holes. This design is inspired by Dr. C M Güralp's 40 years of experience in the geophysical event detection industry.
In the 1970's and 1980's Dr. Güralp set out the standards for miniature surface and borehole broadband seismometers. The first post-hole broadband seismometer was installed in 1987 By Dr. Güralp to monitor underground explosions.
The post-hole Broadband Feedback seismometer is based on orthogonal three axis low noise sensor modules with double nested feedback loop topology. The suspension system is based on the principles of “elastica”.
The ALPHA family of sensors are three component low noise feedback velocity output Broadband seismometers suitable for local, regional and teleseismic recording.
- Single or large scale seismic networks
- Post-hole seismology
- Micro-seismic monitoring
- After-shock monitoring
- Permanent reservoir monitoring
- Induced seismicity detection
- Explosion monitoring
- Hydrocarbon exploration
- High quality digital broadband data output
- Covers complete seismic spectrum with a single transfer function
- Particularly low noise at high frequencies compared to other broadband sensors
- 8 Channel 24-bit internal digitiser
- 9 extra State of Health (SOH) channels
- Programmable Gain Amplifiers on all 24-bit channels
- Remotely configurable and controllable sensor functions
- Automatic centering based on mass position offset
- Suspension system with high cross axis rejection
- Broadband data with high frequency response extending 150 Hz
- Automatic self-installation and zeroing for quick installation
- Tilt tolerance of ±5 degrees
- Portable and easy to deploy
- Waterproof casing with stainless steel connector
- Polyurethane cabling potted to the stainless steel connector
The mechanical sensor orientation is Non-Galperin with -75 dB cross axis rejection on all axis.
The sensor's frequency response covers the complete seismic spectrum with a flat frequency response (no peaks) from 0.008333 Hz (120 seconds) to 150 Hz.
A precision 24-bit 8-channel digitiser is housed inside a waterproof enclosure.
9 extra State of Health (SOH) channels provide comprehensive state of health information of the post-hole sensor.
A truly portable rugged seismometer with fine pitched adjustable feet manufactured from phosphor bronze.
The sensor can be operated with ±5.0 degrees of tilt, and microprocessor controlled remote centering is provided.
Galvanically two stage isolated electronics. The sensor's mechanical section and the feedback electronics sections have their own isolated and hermetically sealed enclosures.
Remote electronic mass locking and unlocking facility, with serial interface for sensor control and parametric sensor data.
All outputs and digital inputs are transient protected.
The noise level of the Alpha Light sensor crosses the New Low Noise Model (NLNM) (below) from 18 Hz to 50 seconds period.
Installation and orientation tools are provided to install the sensor to depths of 5 to 10 metres. The T bar installation tool attachment on the top of the sensor housing is a backlash free bayonet interface.