ABOUT

Gaiacode is a science based, forward looking, innovative company designing and building the next generation of seismic instrumentation.

Our sensors are based on completely new design concepts for their mechanical components, and on major improvements to the feedback systems. The results of these innovations are-

  • Huge increases in the bandwidths of the instruments
  • True recordings of the three degrees of freedom of ground motion
  • Repeatable, cost effective manufacturing of high quality seismic instruments

Although Gaiacode is a young company some of its senior personnel have been an integral part of the development of broadband (BB) seismic sensors over four decades. The major milestones of this group are-

  • 1987: CMG-3T, the first fieldworthy three component BB feedback instrument worldwide
  • 1987: CMG-40T, the first compact three component BB feedback instrument not requiring locking and centering.
  • 1989: Design and production of the first broadband Ocean Bottom Seismometer deployed in a submarine borehole worldwide

Gaiacode is continuing this legacy of developing and realizing new concepts of seismic sensors on a commercial scale. Amongst our latest developments are

  • New suspension systems for the inertial sensor mass, resulting in a truly rectilinear motion.
  • New design concepts for the springs involved.
  • Major improvements in the feedback circuitry.

These recent developments allow us to offer three families of next generation seismic feedback sensors:

  • The ALPHA instruments are our flagship products: low intrinsic noise, very broadband and highly sensitive three component seismic sensors.
  • The THETA instruments are medium motion broadband sensors based on the new suspension design.
  • The SIGMA instruments are robust, compact three component accelerometers similarly based on the new suspension design.

Where it all began

History

At GaiaCode, our founder Dr Cansun Güralp, invented the first-ever Feedback Broadband sensor with the following features:

  • Vertical feedback broadband sensor module with 89 mm diameter
  • First feedback broadband sensor that used triangular spring with fine anchoring wire (patent number: {7909570 (19 March 1979)}, USA patent (4,280,206, July21-1981)
  • First feedback broadband sensor that used capacitive differential displacement transducer with electromagnetic force transducer
  • First feedback inherently digital broadband feedback seismometer patent: UK: (2,144287A 17 July 1984)
  • First borehole sensor with an 89 mm diameter
  • First broadband vertical modular sensor with an 80 mm diameter, for a borehole sensor casing of 89 mm diameter
  • First broadband feedback seismic sensor which had a frequency response extending from DC to 30 Hz

Since the design of the first feedback broadband sensor with the above technical features a fundamentally novel and innovative Broadband feedback sensor concept has been introduced based on triangular (C spring) used in elastic mode in a zero spring topology.

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GaiaCode - Seismic Instrumentation

Our founder

Dr Cansun Güralp

Founded in 2019. GaiaCode marks Dr Güralp’s return to academic and industrial seismometer manufacturing, 40 years after he first revolutionised the industry with the world's first ever broadband miniature feedback instrument.

In 1978 he patented a mechanism that used a triangular leaf spring anchored to a rotational point. In combination with a sensor mass of less than 120 grams and a differential capacitive displacement transducer, this ushered in a new era of seismic instrumentation.

Dr Güralp is once again bringing a novel range of seismometers to the market, making best use of cutting edge material and electro-mechanical design to make further advances on behalf of seismology, science and society.

GaiaCode Founder - Cansun Güralp
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References

  • Ref 1 USHER, M.J., BURCH, R.F. and GURALP, C.M., “Wide-band Feedback Seismometers”, 1979. Physics of the Earth and Planetary Interiors, 18: 38-50.
  • Ref 2 M,J, USHER and C.M. Guralp, “The design of miniature wideband seismometer” Geophys. J.R. ast. Soc. (1978)-55 (605-613) ,
  • Ref 3 GURALP, C.M., “The Design of a Three-component Borehole Seismometer”, 1980. Ph.D. Thesis, Univ of Reading.
  • Ref 4 GURALP C.M. Patent Application, No: 7909579 Filed: 19th March 1979 (declaration priority from Appln No: 10279/78 Filed: 15th March 1978) “Vertical Seismometer”.
  • Ref 5 GURALP C.M. United States Patent Application Number: 4,280.206 March 1979. SEISMOMETERS.
  • Ref 6 GURALP C.M. UK Patent Application GB 2-144-287-A. July 1983 Analog-to-digital converters for Seismometers. The National Research Development Corporation (UK)
  • Ref 7 GURALP C.M. UK Patent Application No. 1900719.4; Title: Infrasound Detector [M&S-IRN.FID4315516]

Precision Calibration of Seismic Sensors

Seismic feedback sensors offer a unique opportunity to perform precision calibration on such devices.

At their core is an inertial mass attached to a suspension system with one degree of freedom. The position and the motion of the mass are detected by a primary transducer, usually a capacitor or a linear variable displacement transformer (LVDT). In addition, the inertial mass has a secondary transducer, typically a coil/magnet arrangement which converts the electronic information generated by the feedback loop into a mechanical restoring force acting on the mass.

At Gaiacode we use the coil constant of the feedback coil as the main parameter for calibrating all our broad-band sensors, which have a high loop-gain. The first calibration step is to tilt the sensors (both vertical and horizontal) on a precision tilt table. Using an 8.5 digit multimeter and precision angle measurement we can calculate the coil constant in units of A/m/s2 with an accuracy of better than 1 part in 10000.

Knowing the coil constant we then inject a wide range of frequencies into the coil using a high precision signal generator and measure the reaction of the mass to this input using the primary transducer.

This procedure gives us a precise measurement of the sensor's output sensitivity value or its frequency response in amplitude and phase, depending on the type of calibration signal injected. In addition, these measurements also evaluate the system linearity and the total harmonic distortion to ground signals.

In this paper we describe the details of this calibration technique and give examples of measurements for systems with responses both in velocity and acceleration.

Author: Cansun Guralp (Gaiacode)