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  Gullfaks C Seismograph Site Evaluation  

  Project documentation

30 October 2012


In cooperation with Statoil we wish to place (temporarily) a seismometer on one of the three concrete platforms on the Gullfaks field. The seismometer will be positioned at the bottom of a platform leg.

Gullfaks-C concrete platform in 216 m water depth

Gullfaks-C concrete platform in 216 m water depth (image source)

Overview, Gullfaks oil field - click to enlarge
Overview Gullfaks oil field - click to enlarge (source: NPD Fact Map)
Gullfaks oil field extension and shape, Gullfaks A/B/C platform locations]]
Gullfaks oil field extension and shape, Gullfaks A/B/C platform locations (source: NPD Fact Map)


Bottom of Gullfaks C platform shaft is classified as Zone 1:

A place in which an explosive atmosphere consisting of a mixture with air of dangerous substances in the form of gas, vapor or mist is likely to occur in normal operation between 10-1000hrs per year. (Source)

2.1 Ex-d enclosure, electrical plug

Ex d enclosure, Bartec Technor AS, model TNBCD453531
Ex d enclosure, Bartec Technor AS, model TNBCD453531

Stahl plug model no. 8570


3.1 Overview

The seismometer we use is Güralp model 6TD, a stand-alone unit that combines 3-component sensors, GPS input for time stamping, digitizer and recorder in one small cylindrical package.

The instrument requires 75 mA @ 12 Vdc input (without GPS attached). Mains voltage available is 230 Vac, so a AC/DC power supply will be needed.

Seismometer and AC/DC power supply will be mounted inside an explosion proof Ex-d container.

If mains supply disappears an Uninterruptable Power Supply (UPS) will provide 60 minutes of operation.

Güralp Mod. CMG-6TD
Seismograph Güralp Mod. CMG-6TD.
Güralp seismometer mod. 6TD mounted in EEx-d enclosure. Click to see pictures

Güralp seismometer mod. 6TD mounted in EEx-d enclosure. Click to see pictures.

3.2 Specifications

Specifications (subset of relevance here; source here):

Parameter Value
Sensitivity 2000 V/m/s
Nominal output sensitivity 2.0 × 10-9 m/s/count
Standard output format 24-bit
Noise-free resolution (NPR) at 20 samples/s > 132 dB r.m.s. (> 22 bits)
Standard frequency band 0.033 Hz (30 s) – 100 Hz
Operating temperature range –10 to +75 °C
Pressure jacket material Hard anodized aluminum
Sensor base plate Hard anodized aluminum
Base diameter 154 mm
Sensor height 242 mm (including handle)
Sensor weight 3.0 kg
Voltage requirements 10..24 V using 12 V DC/DC converter
Current at 12 V DC with GPS 165 mA1)
Nominal current at 12 V DC without GPS 75 mA2)

1) GPS not used. We will use 75 mA in power estimates.
2) Ref. page 16 in GMG-6TD Operator's Guide, Issue D.

We will probably alternate between two nearly identical instruments, Serial numbers T6303 (512 MByte memory) and T6278 (4 GByte).

3.3 Calibration sheets T6303, T6278

  1. Model CMG-6TD-0003, S/N: T6303 - Calibration sheet
  2. Model CMG-6TD-0001, S/N: T6278 - Calibration sheet

3.4 Instrument firmware versions

3.5 Data storage capacity

Both seismometers will be upgraded to 8½ GByte memory.

Güralp has found that, on average, three 100 samples per second streams consume around 50MB of storage a day.

By this rule, 8½ Gbyte should provide six months of storage.

3.6 Seismometer frequency response plots (typical)

See also calibration records in section above.

6TD typical frequency response plot (magnitude & phase)
6TD typical frequency response plot (magnitude & phase)

4 230 Vac -> 12 Vdc POWER SUPPLY

ELC - AL911AE-12V-1A
ELC - AL911AE-12V-1A AC/DC power supply.

Power supply selected:

Even though the 6TD uses less then 100 mA (no GPS) we specified a supply capable of 1 Amp output to handle any peak currents at start-up. In addition, it's a linear supply with very low ripple voltage and good load/line regulation figures.


  • Ex-Zone: 1
  • Power consumption of 6TD seismometer (without GPS): 75 mA @ 12 Vdc supply -> 0.9 W
  • AC/DC power supply (linear), efficiency: 50%, which means that total power consumption can be set to 2 W.


In addition to storing data internally, the 6TD seismometer also transmits serial RS232 data. If we could capture and store these serial data we would achieve an added layer of data security.

This serial data capture device can either share space with the seismometer inside the Exd enclosure, or be placed external to the container - provided there is a signal cable available. The first alternative seems most realistic. In the following some solutions will be outlined.

6.1 Data backup unit within Exd-container

We are looking for a device which simply captures incoming RS232 serial data stream and dumps them onto e.g. a SD memory card. Requirement summary:

  1. Powered from 12 Vdc source, draw < 100 mA current.
  2. Capture serial data at 38400 bits/second.
  3. Requires minimum customization or programming.
  4. Should be DIN rail mountable and require minimal mechanical adaptation.

There are several options available:

6.2 Open Log

6.3 Log-o-matic

6.4 SD memory "Shields"

It is possible to attach what is called "shields" to some common rapid prototyping family of controllers, like Arduiono and Mbed, see next section ...

6.5 MBED controller module (internal)

The MBED is a microcontroller module that has been used successfully in some department projects.


  • Web page LPC1768
  • For rapid prototyping
  • Web based C/C++ compiler
  • Extensive software libraries, also for memory cards. FAT 16 at least -> 2 GByte
  • Mounted on DIN rail bracket

6.6 External backup

6.6.1 Using "Scream" software for data storage

If serial RS232 data signal lines already exists, these can be used to transfer data to laptop placed in nox-ex zone area. In that case, the "Scream" software manufactured by Güralp can be used for data logging.


An external GPS is normally attached to the 6TD seismometer for time stamping purposes.

It is important to notice that the GPS signal consists of two parts: a) An RS232 ASCII data stream, with time, position and other information, and b) a pulse, aptly denoted PPS = "Pulse er second", whose leading edge is synchronized within narrow borders, to start of a new second.

This means that the task of forwarding signals from a remote GPS which is necessary when the seismometer is placed in area where reception of GPS is obstructed - as in our case - gets more complicated. In addition to the serial RS232 data, the PPS must also be transmitted over longer distances.

7.1 Instrument GPS-port

One connector on the instruments servers several purposes: GPS input (both RS232 serial and PPS (Pulse per second), power input, data output, as described below.

Connector pin-out Cable connector details

Instrument connector.
19-pin plug MIL-DTL-26482, typical P/N: 02E-14-19P

Instrument output port, pin designation.
Mating cable connector [typical P/N: ***-14-19S]. Connector pin-out:
Ref. p. 8 in Amphenol "Miniature Cylindrical Connectors" datasheet.
Insert arrangement 14-19. Front face of pin insert.
Insert arrangement 14-19. Front face of pin insert.

Front face of pin insert illustrated.

Supplier: ELFA

Supplier: Farnell


8.1 Data

8.2 T6303 (512MB)

FireWire disk used:

  • Mfr: Maxtor
  • Model: 5000DV
  • Data sheet: Data sheet
  • Capacity: 200 GByte
  • S/N: Y60EQPRE

#### --- WARNING --- ####
It can take log time to mount the disk when it is attached to the 6TD seismometer, and to obtain content listing when it is attached to a PC.

The other FireWire disk (used during readout of data in SFC project) now seems defective.

DIR command before data transfer.
  1. Baud rate is 19200
  2. Start terminal session with seismometer
  3. Execute DIR command to verify that disk is mounted
  4. Extract all data stored in seismometer flash by executing FLUSHALL command.

After data extraction is completed, the result of a new DIR command will be:

DIR command after data transfer.

So data seems to have been transferred successfully to the FireWire disk. We now need to transfer them to PC, so we use the disks USB connector.

Windows Explorer reports that the disk is not formatted - we have to use a program from Güralp to extract data - gcfxtract

gcfxtract software to extract data from external hard disk using Güralp file format system.


9.1 7 June 2012

9.1.1 S/N: T6303 - 512 GByte

Click to enlarge.

9.1.2 S/N: T6278 - 4 GByte

Click to enlarge.

9.2 11 June 2012

9.2.1 S/N: T6303 (512 MB)

Click to enlarge.

9.2.2 S/N: T6278 (4 GB)

Clock check: 4 seconds behind UTC.

Click to enlarge.

9.3 12 June 2012

As two seismometers will be deployed alternately, we wish to be certain that time stamp of data is identical on the two units.

However. there is a time synchronization issue we have to clarify before deployment.

9.3.1 Time synchronization

In order to check correct time stamping of data, we first synchronize the two instrumentation systems (each consisting of 6TD seismometer and laptop) to UTC time in this manner:

  1. The PC laptops running scream are synchronized to UTC by opening "Date and Time Properties" window and clicking "Internet Time" tab. It looks like this on an WinXp machine. Notice that the same time server is used on both machines - "":

    Obtaining time synchronization on Win XP machine.
    Obtaining time synchronization on Win XP laptop.

    Click to open window displaying current UTC time.
    Verifying time setting by comparing with official US UTC time Java applet. (Click to open).

  2. The 6TD seismographs are set to UTC time by opening terminal window and issuing the SET-RTC command.
    Güralp mod. 6TD seismometer: Setting real-time clock from terminal window.

  3. Confirm 6TD clock setting by issuing TIME? command.

  4. Turn off both seismometers and laptops. Power on laptops and confirm that PC time is synchronized to UTC (OK). Power on both seismometers, and confirm that clocks are still synchronized to UTC (OK).

  5. So all clocks should now be synchronized to UTC. But it turns out that time stamping of the same event differ by 14 seconds.

9.3.2 14 second time stamp discrepancy between T6303 and T6278

9.3.3 S/N: T6303 (512 MB)

Click to enlarge.

9.3.4 S/N: T6278 (4GB)

Click to enlarge.

9.4 14 June 2012

Both Units Under Test (UUT) placed on concrete pillar in Seismolab, Realfagbygget, adjacent to NNSN-Bergen STS-2 sensor. North-south axis aligned with compass N/S.

9.4.1 Data recorded on laptops

9.4.2 T6278 (4GB)

6TD clock is 3 seconds behind UTC time (as seen by opening terminal window and issuing CLOCK? command).

Click to enlarge.

9.4.3 T6303 (512MB)

6TD clock is 4 seconds behind UTC time (as seen by opening terminal window and issuing CLOCK? command).

Click to enlarge.




List of documentation.

Item No. Document no. Title Issued by Date Rev. Link
1 UIBGEO-2012-06-001-A Dokumentoversikt Universitetet i Bergen, GEO 26.06.2012 A Download
2 UIBGEO-2012-06-002-A NORDSOK Z-015, vedlegg H: Dataark for container og utstyr Universitetet i Bergen, GEO 26.06.2012 A n/a
3 TEC-10-ATEX-896472-A EC-Declaration of Conformity (TEC-10-ATEX-896472-A) Technor Bartec AS 01.12.2010 A n/a
4 896472-02-1 Ex d IIB Enclosure, TNBCD 453531
GA drawing with partlist
Technor Bartec AS 22.11.2010 A n/a
5 DNV-2003-OSL-ATEX-0136 EC-Type Examination Certificate Det Norske Veritas 11.07.2003 2 n/a
6 50-BCD-5 User Manual – TNBCD Complete enclosure Technor Bartec AS 09.12.2009 D n/a
7 53-CDX-5 EEx d IIC / IIB Explosion proof enclosures Technor Bartec AS May 2007 B Download
8 8570601300-en Operating Instructions, Stahl plug model 8570 R. STAHL Technology Group 17.06.2009 n/a Download
9 UIBGEO-2012-06-003-A Vedlikeholdsprogram for TNBCD 453531 Ex d beholder Universitetet i Bergen, GEO 26.06.2012 A Download
10 UIBGEO-2012-06-004-A Vedlikeholdslogg for TNBCD 453531 Ex d beholder, SN: 101171 Universitetet i Bergen, GEO 26.06.2012 A Download
Above documents to follow the goods. Documents below as additional information.
11 - ICG 653 / Universal Cable Gland Hawke International - - Link
12 - Seismometer model CMG-6TD Güralp Systems - -
  1. CMG-6TD Datasheet
  2. CMG-6TD Manual
  3. "Scream" software (for laptop): Software manual
13 - AC/DC power supply, mod. AL911AE-12V-1A, data sheet ELC - - Data sheet


Version number By Date Approved by Date Details
0.1 O.M. 30 October 2012 - - Draft version
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Page last modified on November 21, 2016, at 10:49 AM
Electronics workshop
Department of Earth Science - University of Bergen