CMG-3TB

The CMG-3TB three-component broadband sensor provides the excellent noise performance of the CMG-3T in a borehole casing.

Features

Covers the complete seismic spectrum with a single transfer function
Response from 1 – 360 s to 50 – 200 Hz (120 s – 50 Hz standard)
High linearity: >107 dB horizontal, 111 dB vertical (USGS figures)
Over 140 dB dynamic range over the entire passband (USGS figure)
Cross-axis rejection over 65 dB
Sensor axes orthogonal to within 0.1 °
Remote electronic mass locking, unlocking and centring
Waterproof and durable, with ‘O’-ring seals throughout

Case options

Standard 3T with three-jaw hole lock.

Slimline 3T with three-jaw hole lock.

The CMG-3TB can be supplied in a range of form factors to suit the needs of your installation.

For a full assessment of the available options, please contact Güralp Systems, quoting the exact dimensions of your borehole and any special requirements.

Option 1 : Standard modular 3TB

This option uses a sonde with outer diameter 89 mm and a single jaw hole lock. The levelling range for this instrument is ±5 °.

Option 2 : Modular 3TB with extended levelling

This instrument uses individual levelling gimbals to extend the centring range to ±10 ° in a stacked sonde with outer diameter 130 mm.

Instruments with extended levelling can be centred at inclinations up to ±10 °. These instruments have an outer diameter of 130 mm.

Option 3 : CMG-3T with borehole base

For wider boreholes, a standard CMG-3T sensor can be supplied in a borehole casing incorporating a three-jaw hole lock, producing an instrument with an outer diameter of 168 mm.

Option 4 : Slimline 3T with three-jaw hole lock

This option fits the sensor components into a smaller package of 150 mm outer diameter, again with a three-jaw hole lock. The sensor package is also shorter than for a standard 3T.

Single-jaw hole lock units can be supplied with adapter pieces to enable installation in boreholes of varying width. Three-jaw hole lock units are specially manufactured for each sensor to your specifications.

Customized instruments can also be supplied for use in boreholes which already contain sensors or hole lock equipment.

Other options

Built-in inclinometer with separate control unit
Hybrid response
CMG-3V vertical single-component instrument
Cable strain relief mechanism (standard if a downhole digitizer is not used)
Low temperature borehole sensor with microcontroller to maintain operation down to −55 ° C (more information)

Noise performance

The CMG-3TB uses the same design as the popular CMG-3T instrument.

The plots below estimate the system noise power of the vertical component of the 3T conventional-response sensor. The system noise power, corrected for system response and gain, is shown as a continuous thin line; the circled line is the raw non-coherent power spectrum. The thicker line is the Peterson New Low Noise Model (NLNM).

Measured self-noise of the CMG-3T, vertical component.

The plot below shows earth tides and earth modes recorded by a 360 s CMG-3TB seismometer with 50 Hz high-frequency corner, outputting data at 1 sample/s to a downhole CMG-DM24 digitizer. The raw data has not been filtered or processed in any way.

Earth modes are routinely observed at quiet stations using 3T sensors.

Earth tides recorded by a CMG-3T borehole sensor.

CMG-3TB

Features

Case options

Option 1 : Standard modular 3TB

Option 2 : Modular 3TB with extended levelling

Option 3 : CMG-3T with borehole base

Option 4 : Slimline 3T with three-jaw hole lock

Other options

Noise performance

CMG-3TB news

New borehole instruments for the South Pole

Case study: Authenticating seismic stations at Conrad Observatory, Austria

New borehole array in Africa



Home Products CMG-3T CMG-3TD CMG-3ESP Compact CMG-3ESPD Compact CMG-5T CMG-5TD CMG-5T Compact CMG-40T CMG-6TD CMG-CD24 CMG-DM16 CMG-DM24 CMG-DCM CMG EDU All products Software New installations Customer support About us	CMG-3TB CMG-3TB The CMG-3TB three-component broadband sensor provides the excellent noise performance of the CMG-3T in a borehole casing. 3TB Datasheet 3TB Manual (PDF) 3TB Manual (HTML) 3V Manual Features Covers the complete seismic spectrum with a single transfer function Response from 1 – 360 s to 50 – 200 Hz (120 s – 50 Hz standard) High linearity: >107 dB horizontal, 111 dB vertical (USGS figures) Over 140 dB dynamic range over the entire passband (USGS figure) Cross-axis rejection over 65 dB Sensor axes orthogonal to within 0.1 ° Remote electronic mass locking, unlocking and centring Waterproof and durable, with ‘O’-ring seals throughout Case options Standard 3T with three-jaw hole lock. Slimline 3T with three-jaw hole lock. The CMG-3TB can be supplied in a range of form factors to suit the needs of your installation. For a full assessment of the available options, please contact Güralp Systems, quoting the exact dimensions of your borehole and any special requirements. Option 1 : Standard modular 3TB This option uses a sonde with outer diameter 89 mm and a single jaw hole lock. The levelling range for this instrument is ±5 °. Option 2 : Modular 3TB with extended levelling This instrument uses individual levelling gimbals to extend the centring range to ±10 ° in a stacked sonde with outer diameter 130 mm. Instruments with extended levelling can be centred at inclinations up to ±10 °. These instruments have an outer diameter of 130 mm. Option 3 : CMG-3T with borehole base For wider boreholes, a standard CMG-3T sensor can be supplied in a borehole casing incorporating a three-jaw hole lock, producing an instrument with an outer diameter of 168 mm. Option 4 : Slimline 3T with three-jaw hole lock This option fits the sensor components into a smaller package of 150 mm outer diameter, again with a three-jaw hole lock. The sensor package is also shorter than for a standard 3T. Single-jaw hole lock units can be supplied with adapter pieces to enable installation in boreholes of varying width. Three-jaw hole lock units are specially manufactured for each sensor to your specifications. Customized instruments can also be supplied for use in boreholes which already contain sensors or hole lock equipment. Other options Built-in inclinometer with separate control unit Hybrid response CMG-3V vertical single-component instrument Cable strain relief mechanism (standard if a downhole digitizer is not used) Low temperature borehole sensor with microcontroller to maintain operation down to −55 ° C (more information) Noise performance The CMG-3TB uses the same design as the popular CMG-3T instrument. The plots below estimate the system noise power of the vertical component of the 3T conventional-response sensor. The system noise power, corrected for system response and gain, is shown as a continuous thin line; the circled line is the raw non-coherent power spectrum. The thicker line is the Peterson New Low Noise Model (NLNM). Measured self-noise of the CMG-3T, vertical component. The plot below shows earth tides and earth modes recorded by a 360 s CMG-3TB seismometer with 50 Hz high-frequency corner, outputting data at 1 sample/s to a downhole CMG-DM24 digitizer. The raw data has not been filtered or processed in any way. Earth modes are routinely observed at quiet stations using 3T sensors. Earth tides recorded by a CMG-3T borehole sensor. CMG-3TB news New borehole instruments for the South Pole December 2006 A new-generation CMG-3TB instrument with adaptations for cold conditions is headed for the South Pole as part of a major upgrade to the world's quietest seismic station. Case study: Authenticating seismic stations at Conrad Observatory, Austria March 2006 A three-instrument vault and borehole station using Authentication Modules to provide CD1.0 and CD1.1 data authenticated with strong cryptography. New borehole array in Africa March 2005 Güralp Systems has been chosen to provide the borehole instrumentation for a major new seismic array in Central Africa. More articles on this topic...