SIGMA Downhole

SIGMA Downhole

Product Overview

The unique slim line design of this SIGMA Downhole instrument makes it an ideal versatile accelerometer for both posthole and borehole installations. Its water proof housing with an outer diameter of only 50 mm is rated for depths of up to 300 m in a wet borehole. A single-arm holelock can be added to the stack (see left instrument in photo). An internal three component MEMS accelerometer and a humidity sensor provide additional SOH information about the installed instrument and its inclination.This downhole accelerometer is suitable for deployments in cased or uncased, wet or dry bore- and postholes.

Besides the casing option described here, the SIGMA Downhole accelerometers can also be added to the ALPHA Borehole instruments, resulting in a comprehensive six-component ground motion borehole measuring station.

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SIGMA Downhole

Key Features

Instrument Design

- The three sensors are stacked on top of each to allow for slim design

- All sensor components are made of non-magnetic materials, minimizing noise induced by outside magntic fields

- Single arm holelock can be added

Instrument Characteristics

- Flat frequency response from DC to 400 Hz.

- Four remotely configurable saturation levels between +/- 4g and +/- 0.5g.

- Other options down to +/- 0.05 g available.

- Dynamic range at +/- 2g >170 dB, at +/- 4g >167 dB

- Operational range within +/- 10 degrees of tilt.

- Cross axis rejection >-70 dB.

- Operating temperature range: -20 to 75 deg C.


- Rugged housing made from 316 grade stainless steel

- Weight with hole lock 8.05 kg, without 6.75 kg.

- Dimensions: outer diameter 50 mm, height with holelock 850 mm, without 760 mm.

- Waterproof as per IP68 standard.

 Power and Electronics

- Power consumption 750 mW.

- Power operating range from 9 to 36 Volt.

- The sensor's electronic circuitry is galvanically isolated, protected against polarity switch and voltage transients.

To obtain a detailed data sheet for this seismometer, please contact Gaiacode Headquarters

 Disclaimer: The product specifications and the stated data are subject to change without prior notice.

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  • 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]