Guralp Systems Limited
MAN-MIN-0001 - Güralp Minimus - Technical Manual


1. Preliminary Notes 2. System Overview 3. System description 4. Getting started 5. Advanced system configuration 6. GüVü app 7. Advanced troubleshooting 8. Appendix 1 – Instrument/channel names 9. Appendix 2 – Minimus network ports 10. Appendix 3 – Connector pin‑outs 11. Appendix 4 – Dimensions and drawings 12. Appendix 5 – Güralp Discovery installation 13. I.P. address configuration on PC or Laptop 14. Revision History

Section Index: 5.1. System status 5.2. Station meta-data 5.3. Network configuration 5.4. GDI push (auto-connection) 5.5. QSCD 5.6. Power monitoring 5.7. Data storage 5.8. Data transmission 5.9. Synchronisation of the sample-clock 5.10. Deploy mode: Full power-save 5.11. Configuration and control of connected analogue instruments 5.12. Configuration and control of connected digital instruments 5.13. Settingsensor orientationand depth parameters 5.14. Transforms 5.15. Earthquake Early Warning 5.16. Using a registry 5.17. Updating Minimus firmware 5.18. Import / Export an existing configuration 5.19. Control Centre

Chapter 5. Advanced system configuration

Advanced system configuration control and configuration tools are available by selecting an instrument in Discovery, right-clicking its entry and selecting “View Web Page”. Alternatively, the web interface can be viewed by navigating to the LAN address of the instrument from any common web-browser.

Note: Some changes in the settings require a system reboot to be applied. This is notified on the top right of the Minimus web-page with the message Reboot Required . It is suggested to perform all the modifications and reboot the Minimus when the configuration is completed clicking on any of the buttons.

5.1 System status

The “Status” tab of the web browser interface provides state-of-health information about the Minimus and connected instruments. These parameters are described as follows:

5.2 Station meta-data

Discovery provides a number of flexible station meta-data inputs. These are accessible from the “Setup” tab of the instrument’s web page.

Label” is used in Discovery only and appears in the list of instruments in the main window. The Label can also be edited by right-clicking on the instrument in the main window of Discovery and selecting “Edit Label”.

Station Name, Network Code and “Site Name are all standard meta-data header values used by the miniSEED file format, which will be included in locally-stored miniSEED files (see section 5.7).

5.3 Network configuration

5.3.1 I.P. address and gateway

By default, the Minimus uses DHCP (Dynamic Host Configuration Protocol) to acquire its network configuration but static addressing can be used if required.

To configure static addressing, visit the “Network” tab of the instrument’s Web page and, under “DHCP”, change the mode from “Enabled” to “Disabled” in the drop-down menu. In this mode, it is possible to specify the I.P. address, the NetMask and the address of the Gateway (default router), as shown:

Before any changes made here will take effect, the Minimus must be re-booted. To do this, click the button on the “Data Record” tab.

Note: By default, the static I.P. address assigned to each MinimusMinimus is unique and derived from the specific serial number of the device. These addresses are in the default network for link-local (APIPA) addresses: (in CIDR notation).

The first two bytes of the address, therefore, are always 169.254. The third byte is the equal to the last two characters of the serial number interpreted as a hexadecimal number and then converted into base 10. The forth byte is the equal to the next-to-last two digits of the serial number, also converted from hexadecimal into base 10.

For example, if the serial number of the Minimus is MIN-C555, the preassigned Static I.P. address will be, where

Network settings are also available in Discovery by right-clicking on the Minimus' entry in Discovery's main window and selecting “Edit Network Address”.

5.3.2 NTP (Network Timing Protocol) configuration

Note: Network Timing Protocol (NTP) is only used for setting the system's internal clock at boot-up, it is not used for sample timing. See section 5.9 on page 53 for details about synchronising the sample clock.

However: if neither GNSS nor PTP are available but NTP is locked and the sample clock's time is more than five seconds different from NTP's time, the sample clock will be adjusted (in a step-change) to NTP time.

By default, the NTP server option (located under the “Setup” tab of the instrument’s web page) is set to “Pool” which uses the virtual server pool This accesses a dynamic collection of networked computers that voluntarily provide moderately accurate time via the NTP to clients worldwide.

Alternatively, it is possible to specify the IP address of your preferred NTP server. To do this, select the “Static” option from the “NTP server” drop-down menu, which activates the “NTP IP Addr” setting, and enter the IP address of your NTP server here.

5.4 GDI push (auto-connection)

A Minimus normally acts as a GDI server, where a client initiates a connection in order to pull data from it. This is the mechanism used when the GDI viewer in Discovery is launched.

The "GDI auto-connection" feature enables the Minimus to establish outgoing network connections in order to push data to one or more remote clients, such as Platinum systems or an Earthworm system running the gdi2ew plug-in.

To configure an auto-connection, type either the I.P. address or the host-name of the target client, a colon (':') and the port number (e.g. or, into any of the connection fields in the “Network” tab of the web page.

When auto-connection from a Minimus to a host is configured, the Minimus will attempt to open a connection to the host. If it fails, it will re-try every 60 seconds. A suitably configured host will accept the connection and the Minimus will then negotiate a link and start streaming data.

If the connection drops, the Minimus will attempt every 60 seconds to reconnect.

Note: The default port number for a GDI-link receiver is 1566. Push servers will normally connect to this port. The default port number for a GDI-link transmitter is 1565. Receivers wishing to pull data will normally connect to this port. See Chapter 9 for a list of the network ports used by the Minimus.

5.5 QSCD

The Minimus can push data in QSCD format (Quick Seismic Characteristic Data) to one or more clients, using outgoing network connections.

To configure a connection, locate the QSCD section of the Network tab of the web page, as shown below. Type either the I.P. address or the host-name of the target client into any of the “Server” fields. This will push data using UDP port 9000, which is the default. If you wish to use a different port number, add a colon (':') and the port number to the end of the specification. For example, or

The Minimus does not automatically send all data when using the QSCD protocol. Channels to be transmitted must be selected (in Z/N/E triplets) and each channel passed through a QSCD transform. See section 5.14.13 for details on how to configure this transform.

5.6 Power monitoring

The “Power” tab of the Minimus’ web page provides information about the supply voltage, as measured by the Minimus. The  Minimus+ can be powered using either the power input connector (see section 10.2) or via the Ethernet connection (see section 10.1) using Power-over-Ethernet (PoE). The voltage measured at the PoE input is also displayed here.

5.7 Data storage

MicroSD cards need to be specifically formatted to operate with the Minimus. The cards shipped with the Minimus and with Radian systems are supplied pre-formatted.

Data are stored on the microSD cards in miniSEED format. Each channel is saved as a series of 128 MiB files. Instrument and station meta-data (e.g. instrument response, coordinates, compression type etc.) are stored in "Dataless SEED" format.

The main panel of the "Data Record" tab in the web interface is shown here:

Options for monitoring and configuration of data storage can be found in the “Data Record” tab of instrument web page. This page is organised into three main panels: microSD status, card formatting controls and channel recording configuration.

The names and contents of each file are described in section 8.

Note: When changing a setting in the Minimus web page, ensure that you wait until the page refreshes before changing another setting. This allows time for the previous change to take effect.

5.7.1 Recording status

The MicroSD card and data recording status can be monitored in the upper-most panel of the “Data Record” tab.

The left-hand column provides details of the external (primary, removable) microSD card and the right-hand column shows the status of the internal (backup) card.

Sections of this panel indicate the status of the following:

Note: If the recording status of the cards is marked NOT RECORDING, clicking on or may solve the issue. Note that the quick format simply moves the write-pointer to the beginning of the recording space, hence overwriting any existing data. The full format, in contrast, erases all the existing data (and can take several hours).

5.7.2 MicroSD card re-formatting

The card re-formatting process fills the card with 128 MiB files containing zeroes. Each file is given a temporary, place-holder name. When data are written, these files are renamed and then over-written with data.

There are two methods for card reformatting: “Quick format” and “Full format”. The quick format mode should be used for pre-deployment tests (e.g. stomp/huddle tests) to ensure that the instruments are operating properly. This mode simply marks the existing files as empty without deleting their contents. Full formatting should be used prior to a long-term deployment to ensure that all headers are included and files are fully clean before writing.

The formatting process formats both fixed and removable cards, sequentially.

Note: A series of tests separated only by quick formats can leave some files with residual data in them. This is not normally a problem because a deployment will typically create data-sets longer than any test, over-writing any data remaining from the tests. The miniSEED extractor utility described in section can be used to remove the residual data if they cause any problems. Quick format

Ensure that the external microSD card is correctly inserted. Click the button: a dialogue box will appear to confirm the formatting operation – click on button to continue.

The instrument web page will refresh and return to the “Status” tab. The reformatting operation is now complete. Full format

Ensure the external microSD card is correctly inserted. Click the button and a dialogue box will appear to confirm the formatting operation – click on button to continue.

The process takes several hours: check the status countdown indicators on the top-right of “Data Record” tab.

Caution: Do not remove or insert the external microSD card while formatting is taking place.

5.7.3 Channel recording set-up

In the left-most column, drop-down boxes are available for each channel to either prevent the channel from recording (by selecting the “Disabled” option) or to select a sample rate. (You can stop all channels from recording by clicking the button).

After changing any sample rate(s), the Minimus will need to be restarted before the changes come into effect; this can be done by clicking the button.

A minimal web page is displayed during the reboot and the status LEDs will show the starting-up sequence (see section 3.1.1). Once the Minimus has successfully restarted, the full web browser display/controls will be available again.

5.7.4 Viewing recorded data

The “Storage” tab of the web browser interface displays the miniSEED files stored on the microSD card:

If the web page is accessed from a web browser, clicking on the file from the list automatically starts a download using your browser's standard mechanism:

Note: When viewing the web page from within Discovery's built-in browser, it is necessary to copy the URL for the file (by right-clicking on it and selecting "Copy URL") and then pasting it into a web browser.

The microSD cards are formatted with empty files which are filled with data as they become available. The file-names are also changed when the files are written to. Until they are written to, they are marked as “hidden” files, so that it is easier to see how many files contain data when looking at the contents of the card.

5.7.5 Downloading data for specific time-intervals

Data for a single stream spanning a specific time-interval can be downloaded from the Storage page of the web interface. To do this, start by selecting the desired stream from the drop-down menu:

… then select the start and end dates and times using the pop-up calendars:

Lastly, click the download button to initiate a file transfer using your browser's standard mechanism.

Note: The pop-up calendars are not supported by Discovery's built-in browser. The required dates can simply be typed in or the entire operation can be performed in an external web browser.

5.7.6 Bulk data extraction

To view files saved on the external microSD card, remove the card, as described in section 3.1.4. Insert the card into a microSD card reader (external or in-built) on your PC/laptop. Within a few seconds, the card should appear as a removable disk/drive.

A microSD card formatted for the Minimus contains many "hidden" files. They are created at format time with no contents and then renamed, unhidden and filled with data as required.

When viewing files in Windows Explorer, it may be helpful to configure your system so that "hidden" files are not shown. In Windows 10, this can be done by clearing the “Hidden items” check-box within the ribbon of Windows Explorer.

5.7.7 The contents of the microSD card

The root directory of the disk contains seven items:

The typical contents of the all_miniSEED_files_are_in_here directory looks like this:

The file-name consists of four components:

The “Storage” tab also shows links to five auxiliary files, which are either saved in the Minimus' flash RAM or are dynamically generated:

5.8 Data transmission

The monitoring and configuration of transmitted data is handled using the “Data Stream” tab of the instrument’s web page.

In most-left column, drop-down boxes are available for each channel to either select a sample rate or to exclude the channel from streaming (by selecting the “Disabled” option). All streaming can be stopped by clicking the button.

Upon changing the sample rate, the Minimus will need to be restarted for the changes to come into effect; this can be done by pressing the button.

During the reboot, the LEDs will flash, displaying the starting-up sequence (see section 3.1.1) and the Instrument Web Page will display the following screen.

Once the Minimus has successfully restarted, the full web browser display and controls will be available for use again.

5.8.1 Scream! (GCF format + Scream protocol)

The Minimus can act as a Scream! Server and stream data by sending GCF (Güralp Compressed Format) packets over a network connection using the scream data-transmission protocol.

This is primarily intended to support Güralp’s Scream! Software (see section 4.3.2) or any software that can communicate using the Scream! Protocol, including SeisComP3.

These include:

Data can also be received by software that can communicate using the Scream! Protocol, including SeisComp3 and Earthworm.

Note: Güralp devices running the Platinum software can receive GCF data over the scream protocol, but the GDI-link protocol is preferred in these cases.

5.8.2 GDI-link protocol

The Minimus can transmit data using the GDI-link protocol. GDI-link can currently be used with:

GDI-link provides a highly efficient, low latency method of exchanging data via TCP between seismic stations and data centres. The protocol allows state-of-health information to be attached to samples during transmission. The topology can be many-to-one or one-to many. This means that a receiver can accept data from multiple transmitters and a single transmitter can send data to multiple receivers, allowing maximum flexibility for configuring seismic networks. GDI-link streams data sample-by-sample (instead of assembling them into packets) to minimise transmission latency.

A significant advantage of GDI-link is that it has the ability to stream data pre-converted into real physical units instead of just as raw digitiser counts, obviating a requirement for receivers to be aware of calibration values.

For more information on GDI-link, please refer to Güralp manual SWA-RFC-GDIL.

5.8.3 SEEDlink protocol

The Minimus can act as a SEEDlink server to send miniSEED data packets over a network connection. The SEEDlink server is enabled by default but it can be disabled and re-enabled if desired. The server has a configurable back-fill buffer.

Note: The Minimus SEEDlink back-fill implementation is packet-based.

In the “Network” tab of the Minimus' web-page, select the desired SEEDlink mode:

The choices are:

Note: As a general guide, we find that 139 264 records is normally sufficient to store around one day of triaxial, 100 sps data.

Standard SEEDlink has a fixed packet size of 512 Bytes and each miniSEED packet is completely populated with data before it is transmitted. The Minimus supports a modified version of SEEDlink that allows the transmission of incomplete packets. This improves latency.

Note: The modified SEEDlink is only available for EEW channels - i.e. the main seismic channels (generated with causal low latency filters) and the STA, LTA, STA/LTA ratio channels.

The user can specify the rate at which miniSEED packets must be transmitted. If populating complete packets would result in this rate not being achieved, incomplete packets are transmitted instead. The number of samples in each packet, therefore, depends both upon this setting and on the sample rate.

In the “Network” tab of the Minimus web page select the interval in deciseconds (1 decisecond = 100 ms or 0.1 seconds) between miniSEED packets.

The modified SEEDlink protocol also allows the use of 256-byte records as an alternative to the standard 512-byte format. The “Data Record Size” drop-down menu on the “Network” tab of the Minimus web page controls this behaviour.

Note: Not all SEEDlink clients can accept 256-byte records. Consult your client's documentation if in doubt.

To test the SEEDlink server, Güralp recommends using the slinktool software for Linux, which is distributed by IRIS. For more information and to download a copy, see

To show a list of available miniSEED streams, issue the command:

slinktool -Q IP-Address

Which produces output like the following:

DG TEST  00 CHZ D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  01 HHZ D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  00 CHN D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  01 HHN D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  00 CHE D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  01 HHE D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  00 MHZ D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  00 MHN D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

DG TEST  00 MHE D 2016-09-13 10:42:18  -  2016-09-13 10:46:56

To print miniSEED data records of a single channel, you will need the following command:

slinktool -p -S DG_TEST:00HNZ.D IP-Address

Which produces the following output:

DG_TEST_00_HNZ, 412 samples, 100 Hz, 2016,257,10:43:42.000000 (latency ~2.9 sec)

DG_TEST_00_HNZ, 415 samples, 100 Hz, 2016,257,10:43:46.120000 (latency ~2.6 sec)

DG_TEST_00_HNZ, 416 samples, 100 Hz, 2016,257,10:43:50.270000 (latency ~3.0 sec)

DG_TEST_00_HNZ, 413 samples, 100 Hz, 2016,257,10:43:54.430000 (latency ~2.6 sec)

DG_TEST_00_HNZ, 419 samples, 100 Hz, 2016,257,10:43:58.560000 (latency ~3.0 sec)

DG_TEST_00_HNZ, 418 samples, 100 Hz, 2016,257,10:44:02.750000 (latency ~2.6 sec)

DG_TEST_00_HNZ, 415 samples, 100 Hz, 2016,257,10:44:06.930000 (latency ~3.0 sec)

The SEEDlink server on the Minimus also supports the use of the “?” character as a wild-card within network, station and channel codes. This allows you to request multiple streams using a single command.

Note: Because the ? character has special meaning to the shell, it is safest to quote this character with a preceding backslash ('\') when used in command arguments. MiniSEED extractor

The miniSEED extractor serves two purposes:

The miniSEED extractor reads miniSEED files on the PC and copies them to a selected Destination folder, keeping track of the latest block time-stamp as it goes. If it encounters either an unused block or a time-stamp which is earlier than the previous one, it stops copying, truncating the output file at that point. This guarantees that each output file contains only blocks in time order and contains no wasted space.

To use the tool, select "miniSEED Extractor" from the Edit menu. Click the first button to select which files you wish to process and then the second button to select the folder into which you wish the output files to be written. Finally, click the button to extract the valid data from the selected files into new files in the selected destination folder.

The same tool can also generate a report of any gaps in the data from the input files. To use, select the input files as before and then click to view the report.

5.9 Synchronisation of the sample-clock

The Minimus system synchronises its sample clock using an attached GNSS receiver or, if that is not available, Precision Time Protocol (PTP).

The currently supported GNSS systems are Navstar (GPS), GLONASS and BeiDou. If visibility of the satellite constellation is available, this is the most accurate way to synchronise your digitiser. The Minimus accessory pack includes a combined GNSS antenna and receiver for this purpose: see section 3.2.2 for details.

Precision Time Protocol (PTP) is a network protocol which uses modified network hardware to accurately time-stamp each PTP packet on the network at the time of transmission, rather than at the time that the packet was assembled. If you do not have an existing PTP infrastructure, the simplest way to use PTP is to add a "grand-master clock" to the same network segment as the digitisers. A typical such clock is the Omicron OTMC 100, which has an integrated GNSS antenna and receiver which it uses as its own synchronisation source. PTP timing can be extended over up to 100 metres of Ethernet cable or longer distances when fibre-optic cable is used.

Note: Although Network Timing Protocol (NTP) is used for setting the system's internal clock at boot-up, it is not used for sample timing. NTP is not, in general, accurate enough for this purpose. If it is impractical to use the GNSS receiver for synchronisation, PTP is the only viable alternative.

However: if neither GNSS nor PTP are available but NTP is locked and the sample clock's time is more than five seconds different from NTP's time, the sample clock will be adjusted (in a step-change) to NTP time.

5.9.1 GNSS lock status

This is available in the “Status” tab of the instrument’s Web page.

A number of GNSS reporting parameters are given, including:

5.9.2 PTP (Precision Time Protocol)

The Minimus system supports timing provided through PTP.

The IEEE 1588 Precision Time Protocol is used to synchronise clocks across a computer network. It is significantly more accurate than NTP but generally requires specialised hardware support. PTP can be configured for multicast or unicast mode. In unicast mode, the server IP address must be specified.

This is available in the “Status” tab of the digitiser’s Web page. A number of reporting parameters are given, including: Special notes for PTP with Maris ocean-bottom systems.

PTP is the only source of timing available for a deployed Maris digitiser. To configure, visit the “Network” tab of the digitiser web page.

Under the heading “Network config” are four options:

Select the option “Run always – Override GPS” before the deployment of a Maris cabled system. PTP offset corrections

If your PTP infrastructure produces a fixed offset (when compared with GNSS), a manual correction can be applied to compensate for this.

The required correction value can be extracted from the internal clock from GNSS stream of the Minimus. In the Live View enable the 0CGPSO channel and select at least 20 minutes of data. Right-click on the selection and click on Show Samples:

At the top of the resulting window, the maximum (max), average (avg) and minimum (min) values are displayed:

Note the value of the average, multiply by -1 and enter the resulting value in the PTP Offset Correction box in the Network Timing section of the Network web page.

5.10 Deploy mode: Full power-save

The Minimus digitiser offers two deployment modes: "Normal" and "Full power-save". "Full power-save" mode makes a number of configuration changes in order to reduce the unit's power consumption. This mode is particularly useful when using Maris digital ocean-bottom sensors.

The desired mode can be specified using the “Deploy mode” drop-down menu in the “Setup” tab of Minimus web page. Changes are not applied immediately.

"Full power-save" mode temporarily disables auto-centring of a connected the Maris digital sensor, so that it is not continually re-centring while being lowered to the sea floor. When this mode is selected, the “Auto Centre Disable (hr)” input field appears: use this to specify the length of time before auto-centring is re-enabled.

Note: Güralp recommend a value of 10 to 12 hours to fully cover the entire deployment procedure.

The final step is to click on the button and confirm or cancel the operation from the pop-up window that appears.

A thirty-second count-down will start before the system enters power-save mode. The screen changes and a new button is added:

You can cancel the operation before the countdown is complete by clicking the button.

Caution: The power-save mode will disable the Ethernet and GNSS modules. You will not be able to continue to use the web interface.

Once in deploy mode, the only way to re-enable the Ethernet module is to connect to the Minimus via a serial connection (see section 7) or to use the GüVü Bluetooth app (see section 6.4).

When a serial or Bluetooth connection is established, type the command powersave off in the console to disable the "Full power-save" mode and re-enable Ethernet communication.

5.11 Configuration and control of connected analogue instruments

5.11.1 Setting instrument type

The analogue sensor type is user-selectable and the Minimus includes a choice of several Güralp sensors and accelerometers. If the sensor is not in the list, select “Generic velocity” or “Generic acceleration”, according to the instrument's response.

A reboot is required after this change.

5.11.2 Setting instrument (sensor) gain for Güralp Fortis

The Güralp Fortis strong-motion accelerometer features a remotely-switchable gain option that can be controlled from inside Discovery. First, ensure that the physical gain switch on the underside of the Fortis is set to position “3” (as indicated by the engraving). See MAN-FOR-0001 for more details.

To change the gain electronically, first, set the “Instrument Type” to “Güralp Fortis”. Setting this option will then enable the “Instrument Gain” control. Under the “Instrument Gain”, select a gain setting (options: 0.5g; 1g; 2g; 4g).

Setting the instrument type to “Fortis” will also change the miniSEED channel names to indicate that data are recorded from an accelerometer, e.g. “HNZ”.

5.11.3 Setting digitiser gain

The input gain can be controlled from the "Setup" tab of the web page using the “Input Gain” drop-down box. Digitiser gain options available are: Unity, ×2, ×4, ×8 and ×12.

The input range and resolution change automatically when the gain is selected and the gain in the RESP files and Dataless SEED is updated automatically.

5.11.4 Mass control

The Minimus can lock, unlock and centre the masses of connected instruments. Mass centring

Many broadband seismometers (e.g. Güralp 3T and 3ESPC) support remote/electronic mass centring. Change the polarity of the control signal using the drop-down menu if necessary.

Mass centring can be controlled from the "Setup" tab of the web page using the button. Mass centring status and control can also be found in the Centring tab of the instrument Control Centre window. Mass locking

Some seismometers require their masses to be locked for transportation. Mass locking can be controlled from the "Setup" tab of the web page using the and buttons. Change the polarity of the control signals using the drop-down menu, if necessary.

Note: The mass lock control buttons are not displayed unless the selected sensor type has a mass-locking mechanism.

5.11.5 Instrument response parameters

Calibration is a procedure used to verify or measure the frequency response and sensitivity of a sensor. It establishes the relationship between actual ground motion and the corresponding output voltage. Calibration values, or response parameters, are the results of such procedures.

Response parameters typically consist of a sensitivity or "gain", measured at some specified frequency, and a set of poles and zeroes for the transfer function that expresses the frequency response of the sensor. A full discussion of poles and zeroes is beyond the scope of this manual.

The gain for a seismometer is traditionally expressed in volts per ms-1 and, for an accelerometer, in volts per ms-2. Other instruments may use different units: an electronic thermometer might characterise its output in mV per °C.

A calibration procedure is also used to establish the relationship between the input voltage that a digitiser sees and the output, in counts, that it produces. The results are traditionally expressed in volts per count. Each Minimus is programmed at the factory so that it knows its own calibration values.

Although the Minimus automatically receives calibration parameters from connected digital instruments (e.g. Güralp Radian), calibration values need to be entered manually for connected analogue sensors (e.g. Güralp Fortis).

To enter the calibration values for your analogue instruments, right-click the Minimus in Discovery’s main window and select “Calibration” → “Calibration Page Editor”.

This form has one tab for each seismic component, for the mass positions and calibration channel. The instrument's response values should be entered in the here. These are:

The calibration parameters for one component can be copied to any other component of the same instrument, or other instruments. This is especially useful for poles and zeros, because they are typically identical for all three components of all instruments in a class.

The drop-down menu in the “Component configuration” section allows selection of what to copy: poles and zeros, gains or everything. The destination sensor and component(s) can be selected in the subsequent drop-down menus. Click on the button to copy and paste the selected values. Finally click on button to send the calibration values to the digitiser and save them permanently. Repeat this last step for the other axis. Note that only sends the calibration of the selected axis.

The overall system calibration parameters can be exported and saved in a file for future use by clicking on the button under “System calibration values”.

The resulting file-name will have the extension .conf. Values from an existing calibration file can be imported using the button. The associated drop-down menu allows specification of what to import: poles and zeros, gains or everything. Click on to send the calibration values to the digitiser and save them permanently. Note that this action will only send the calibration of the selected sensor. Click on the button to send the complete calibration to the digitiser.

When transmitting MiniSEED data, the responses of the instruments and digitisers are encoded in a message called a “dataless SEED” volume. The contents of these volumes can be displayed in human-readable form, known as RESP, by clicking on the “RESP file” link of each channel in the “Data flow” and “Data record” tab of the Minimus web page.

Clicking on a RESP file link produces a page like this:

Right-click anywhere and select “Back” to return to the Minimus web-page.

To save a RESP file, right click on it in the main list and select "Save Link":

Note: RESP files are not available for channels that have a transform enabled. For details about transforms, see section 5.14.

5.12 Configuration and control of connected digital instruments

Please refer to Section 7 of MAN-RAD-0001 for full details on configuring and controlling compatible digital instruments, such as the Güralp Radian, connected to the Minimus.

5.13 Setting sensor orientation and depth parameters

5.13.1 Applied rotation

A Matlab extension for Scream! allows easy determination of the exact orientation of a sensor relative to a surface reference sensor (which can be accurately aligned magnetically or geographically. The procedure is explained at

The Relative Orientation extension of Scream! provides a correction angle that can be entered into the Sensor Orientation section of the Minimus web page.

This feature can be applied to analogue seismometers and accelerometers and also to Borehole or Post-hole Radians, when installed with a vertical orientation.

Note: The input rotation is automatically applied to both transmitted and recorded data.

5.13.2 Instrument installation parameters

The Dip (tilt angle from vertical), Azimuth (tilt direction from North) and Depth of analogue or digital sensors connected to the Minimus can be set in the Setup tab of the web interface in the section “Instrument Installation Parameters”. The instrument to which the displayed parameters apply is selected using the drop-down menu.

Note: The orientation and depth are not applied to the data, the parameters are only saved in the Dataless SEED.

5.14 Transforms

The Minimus is capable of applying mathematical transforms to the streamed and recorded data. These include low-pass and high-pass filters, integration, differentiation, rotation, STA/LTA ratio etc.

When a specific transform is activated on a particular channel, the resulting streamed (or recorded, accordingly to the chosen configuration) data output is automatically transmitted and/or recorded with the transform applied. The units-of-measure are re-calculated accordingly.

Transform functions are enabled or disabled from the “Data Stream” and “Data Record” tabs for each channel.

Note: To enable or disable a transform on any channel, it is necessary to reboot the Minimus. Transforms can be applied only on enabled channels.

The available transforms are:

Some transforms require parameters such as frequencies or coefficients. For these, the user can either use a fixed, default set, or create their own custom set.

To use customised parameters, visit the “Transform” tab and select the “Saved User Parameters” option in the “Parameter Source” drop-down menu. Type in the required parameters and then click to store them. It is possible to switch between Default and Saved User Parameters without altering the stored custom parameters but clicking while “Default parameters” is selected will overwrite the customised parameters with the default values.

The various transforms are each described in the following sections.

Caution: The button at the top of the "Transform" column does not disable transforms for all streams. It stops transmission of all streams, which may not be what you intend.

5.14.1 Pass-through

This null transform simply outputs a copy of the input data, without applying any transform. It has no configuration parameters.

Note: This transform is selected by default when transforms are first enabled or when an invalid transform is selected. Do not use pass-through as a method of disabling transforms: instead, select "Disable transforms" from the drop-down menu next to each stream on the "Data Streams" tab,

5.14.2 Differentiation

This transform differentiates the input data, e.g. if the input is a velocity (ms-1) channel, the output will be acceleration (ms-2). It has no configuration parameters.

5.14.3 1st order LPF

This transform applies a first-order low-pass filter to the input data.

The single configurable parameter is "Corner Frequency": this specifies, in Hz, the frequency at which the output power is attenuated by -3 dB. Above this frequency, output power is attenuated by a further 6 dB per octave or 20 dB per decade.

5.14.4 2nd Order LPF

This transform applies two sequential first-order low-pass filters to the input data.

The single configurable parameter is "Corner Frequency": this specifies, in Hz, the frequency at which the output power is attenuated by -3 dB. Above this frequency, output power is attenuated by a further 12 dB per octave or 40 dB per decade.

5.14.5 1st Order HPF

This transform applies a first-order high pass filter to the input data.

The output is the difference between a low-pass filtered copy of the signal and the unfiltered signal.

The single configurable parameter is "Corner Frequency": this specifies, in Hz, the frequency at which the output power is attenuated by -3 dB. Below this frequency, output power is attenuated by a further 6 dB per octave or 20 dB per decade.

Note: The high-pass filter is implemented by subtracting the output of a low-pass filter from the unfiltered data:

5.14.6 2nd Order HPF

This transform applies two cascaded first order High Pass Filters to the input data.

The output is the difference between a low-pass filtered copy of the signal and the unfiltered signal.

The single configurable parameter is "Corner Frequency": this specifies, in Hz, the frequency at which the output power is attenuated by -3 dB. Below this frequency, output power is attenuated by a further 12 dB per octave or 40 dB per decade.

Note: The 2nd-order high-pass filter is implemented by subtracting the output of two sequential 1st-order low-pass filters from the unfiltered data:

5.14.7 2nd Order biquad

This transform applies a second-order bi-quadratic filter to the input data.

The biquad filter is a second-order recursive linear filter, containing two poles and two zeros. In the Z-plane, the transfer function is the ratio of two quadratics in z, as shown.

The two configurable parameters are:

5.14.8 Integration

This transform integrates the input data, e.g. if the selected channel unit is velocity (ms-1), the output produced is displacement (m).

The integration transform is implemented as a configurable chain of three components:

The configurable parameters are:

5.14.9 Double Integration

This transform integrates the input data twice so, for example, if the selected channel is acceleration (ms-2), the output produced is displacement (m).

Analogously to the single integrator, the double integrator applies an initial DC high-pass filter and then two further high-pass filters, one at the output of each integrator. The high-pass filters are implemented using an LPF and a subtractor, as described in section 5.14.5.

The configurable parameters are:

5.14.10 EEW Parameter Observer

When an EEW trigger occurs (or is simulated -see below), the peak ground motion values (Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV) and Peak Ground Displacement (PGD)) are calculated and automatically recorded over the selected time-window and subsequently transmitted as a CAP message (see Section 5.15 for more details). This transform allows the operator to directly observe the PGA, PGV or PGD values during a configurable time-window of data. It is available for use with both velocity and acceleration input signals.

Note: This transform is intended to be used in conjunction with the Earthquake Early Warning (EEW) system. It should only be applied to low-latency, causal-filtered seismic channels (e.g. 0VELZC, 0AXLNC, etc.) that are used for EEW triggering.

The implementation of the transform differs, depending on whether the input stream represents velocity or acceleration data.

The high-pass filters are implemented using an LPF and a subtracter, as described in section 5.14.5.

The configurable parameters are:

Note: Güralp recommend using the integration (section 5.14.8) and double integration (section 5.14.9) transforms to test the filter parameters, because the effect of the parameters will then be clearly visible in the transformed streams. Once suitable parameters have been determined, they can be copied to the EEW Parameter Observer transform.

Note: For testing purposes, a trigger can be simulated by setting the "Restart" option to 1.

5.14.11 STA/LTA Trigger

The Earthquake Early Warning system (EEW) compares the ratio of a short-term average (STA) to a long-term average (LTA) in order to detect "trigger" conditions. For more information see Section 5.15.

This transform is included to help determine parameters for configuring the EEW system. It does not affect the operation of the EEW system in any way. The transform calculates the ratio between the result of the Short Term Average filter and the Long Term Average filter. The input signal is passed through a high-pass filter which removes any DC offset.

The configurable parameters are:

The high-pass filter is implemented using an LPF and a subtracter, as described in section 5.14.5.

5.14.12 Three-dimensional rotation

This transform rotates three velocity/acceleration seismic components in space. Rotations are represented by unit quaternions (in preference to the more usual Euler angles: yaw, pitch and roll) because they are unambiguous and avoid the problem of gimbal lock.

Note: The rotation transform can only be applied if it is enabled in all three velocity/acceleration components of a single instrument at the same sample rate.

Any rotation in three dimensional space can be represented as a combination of a unit three-dimensional vector, u⃗, which specifies the axis (and sense) of the rotation, and a scalar angle, θ, which specifies the amount of rotation

Güralp follows a North, East, Up convention when describing sensor orientation. Using this convention, we can represent u⃗ as [u,v,w] and use Pauli's extension to Euler's formula:

to form a quaternion: where:

For example, a perfectly- oriented sensor has a (null) rotation of , where the sensor's Z, N and E axes align with the North, East and Up global axes.

A rotation of

represents a sensor that has been rotated 90o about its x axis to align the sensor's Z, N and E axes with global North, Down and East respectively.

Note: Clockwise rotations, when looking along an axis, are denoted as positive. This is generally known as the "right-hand rule" because, if you point your right thumb along the (directed) axis, your fingers will curl in a clockwise direction about it.

In the degenerate case of a simple rotation about a vertical axis (commonly used to correct data from a misaligned borehole instrument), the axis of rotation is vertical, so our unit vector is [0,0,1] (following the "North, East, Up" convention). To rotate by θ (where positive θ is clockwise when looking upwards), our quaternion should be:

As a final check, note that

which satisfies our requirement for a unit quaternion. The parameters to enter in the Configure Transforms fields are, therefore:

Scalar, X ⇒ 0 , Y ⇒ 0 and Z

5.14.13 QSCD (triplet)

The QSCD protocol (Quick Seismic Characteristic Data) transmits values computed from the three triaxial streams of an instrument. One packet is transmitted every second so the number of samples in each packet is equal to the sample rate of the three input streams.

QSCD calculations are implemented using transforms and configured via the Data Stream tab of the Minimus web page. The three input channels must all be configured with the QSCD (triplet) transform. (The transform is disabled if the sample rates of the input streams do not match.)

In the Transform tab, the parameter “Period length” configures the number of samples to include in a QSCD packet. For example, QSCD20 requires the sample rate of the streams to be 20 sps so the “Period length” must be set to 20 (samples), in order to send a packet every second.

5.15 Earthquake Early Warning

The “Trigger” tab is dedicated to Earthquake Early Warning settings. These are disabled by default because of the amount of processing resource – and hence, power – consumed by triggering calculations. When enabled, the causal filtered taps are visible in the “Data Stream” tab.

The Earthquake Early Warning subsystem can be enabled using the drop-down menu at the top of the "Trigger" page of the web interface.

The heart of the Earthquake Early Warning subsystem is an STA/LTA (Short-Time-Average divided by Long-Time-Average) triggering algorithm. The algorithm continuously calculates the average values of the absolute amplitude of a seismic signal in two simultaneous moving-time windows. The short time average (STA) is sensitive to seismic events while the long time average (LTA) provides information about the current amplitude of seismic background noise at the site. When the ratio of STA to LTA exceeds a pre-set value (the parameters can be set, as seen in the picture below), an event is “declared”.

The following parameters can be configured:

When a trigger is declared, the system will issue messages using the Common Alerting Protocol. For the full specification of this protocol, please refer to

Various parameters control how the CAP message is created.

These are:

The Triggers section of the web page enables the user to configure the triggering system. The trigger source should be configured first because different configuration options are displayed for different source types. Once the source-specific settings are configured, the destination should be specified. Destinations can be shared between sources, allowing the creation of networks (directed graphs) of systems for distributed event detection. EEW parameters to be sent in the CAP messages can be enabled only for one source that belongs to each sensor. The EEW parameters sent are PGA, PGV and PGD values and they have to be configured in the “Transform” tab (see section 5.14.10).

5.15.1 Trigger sources

The available sources are listed below, along with the configurable fields available in each case.

5.15.2 Trigger destinations

The options available form the various Destination fields are:

5.15.3 Derived Streams

The various calculated averages used in the triggering algorithm can be displayed as streams in Discovery’s live streaming window. These streams are visible only if the trigger is enabled. This can be used to help decide appropriate triggering parameters. The available streams are:

Note: Each time an event is detected and the trigger is enabled, the LED on the top of the Minimus will flash blue once.

5.15.4 CAP receiver

Güralp Discovery includes a CAP (Common Alerting Protocol) receiver. It listens on a specified UDP port for incoming CAP messages. When one arrives, it is displayed and plotted on a map. In addition, the receiver can open a TCP connection to the cloud-based registry server and display CAP messages that have been sent to the registry server. See section 5.16 for information about configuring a registry server.

All CAP messages can be stored in a log-file. The full message is recorded so that it can be re-loaded later, if required.

The CAP receiver functionality is accessed using the context (right-click) menu in Discovery or clicking on “Edit” in the menu bar:

The CAP receiver window allows specification of the listening port. Each Minimus from which messages should be received must have this value specified as the “CAP Port” in its triggering settings (see section 5.15.2). The value should be between 1025 and 65535. You should avoid numbers in the list at

The reception of CAP messages can be enabled or disabled clicking on the button at the top, right-hand side of the window.

If you wish to forward the CAP messages to a server, type its IP address into the field and tick the check-box named “Use forwarding server”. An error message is displayed if the entered IP address is not valid.

To log CAP messages to a file, tick the “Log events” check-box and use the button to select an appropriate location for the database file.

To import an existing database of events, first enable logging, then browse to the file using the button and, finally, click the button to load the file. If no file is specified, the logging is automatically switched off and a pop-up message is displayed.

When an event is detected and a CAP message is received, the location of the Minimus that generated the trigger is identified by a pointer displayed on the map. The events and the information contained in the CAP message are displayed at the right-hand side of the window. This includes the SEED identifiers, network, station, channel and location, along with the time, the recipients and the threshold value which was exceeded.

If the EEW parameters are enabled in a particular source, after the first CAP message containing the event information, three other messages with the PGA/PGV/PGD details are sent, one for each component.

Click on the button to clear markers from the map and descriptions from the right-hand-side list. This action does not affect the contents of the log-file.

5.15.5 Seismic Event Table

The Minimus can generate a “Seismic Event Table”. This is list of events detected by the STA/LTA transforms. It contains information about the time when the event occurred, its duration, the channel that generated the trigger and the peak magnitude of the event. The seismic data before, during and after the event are saved in miniSEED format and can be downloaded using links in the table.

The table is located at the bottom of the “Trigger” tab in the Minimus web page.

Events will only appear in the list if one or more channels have been transformed using the “STA/LTA Trigger” transform (see section 5.14.11 on page 79 for more details).

Note: The Seismic Event Table is independent of the main triggering settings. Even if the EEW trigger is disabled, the table is still populated if STA/LTA transforms are enabled on any channels. The parameters of the STA/LTA calculations are configured via the “Transforms” tab. In order to obtain consistent lists of events detected using both the EEW trigger and the event table, we recommend setting the same parameters in both the "Trigger" tab and the "Transforms" tab.

The Minimus allows the download of event data in miniSEED format in a time range that is user selectable. The user can select how many seconds before and after the event detection to include in the miniSEED file.

The event table shows which of the components has caused the trigger and the user can chose to either download data related to that single component by deselecting the option “Download Z, N, E Triplet” or download data for all three components by leaving the option enabled.

The last column of the table contains links to downloaded and saved miniSEED files related to each event.

5.16 Using a registry

Discovery can maintain a list of Minimus digitisers in a local or cloud-based registry, simplifying management of medium to large networks and removing the need for static IP addresses at telemetered stations. Registered digitisers appear in the selection list in the main screen, regardless of whether they are on the local network or not.

Administrators can create their own registry servers by installing a simple program on a server. The server itself must have a static IP address and be accessible to all connected Minimus units, as well as the PCs running discovery. Registry servers programs are currently available for Linux and Windows. Please contact Güralp technical support for details.

For administrators not wishing to install their own registry, Güralp provide a shared registry server in the cloud at which customers are welcome to use.

Registered digitisers must be assigned to groups, each of which has a Group Identifier. Instances of Discovery must also be configured with a Group ID and can only display registered digitisers from the matching group. This allows partitioning of large networks into smaller administrative domains. It also makes possible the simultaneous use of the Güralp shared registry server by multiple organisations.

To use a registry:

5.16.1 Configuring a Minimus for use with a registry

The address of the registry server and the chosen Group ID must be set individually for each participating Minimus digitiser.

To do this, first connect the Minimus to the same network as a PC running Discovery and click the button, so that the Minimus appears in the main Discovery list. Right-click () on the digitiser’s entry and select “View Web Page” from the context menu:

In the resulting web page, select the “Network” tab. The Registry parameters can be found near the bottom of the resulting screen:

These are:

Once you have set the correct values, the digitiser must be rebooted before they will take effect. To do this, click the button.

5.16.2 Configuring Discovery for use with a registry

To specify a registry server for an instance of discovery, type its address into the field at the bottom left of the main screen:

To set the Group ID in Discovery:

Return to the main windows and test the configuration by clicking the button. All Minimus digitisers using the same Registry server and Group ID should appear in the main list.

5.16.3 Registry mode: using WAN or LAN addresses

When Discovery displays a list of devices found from a local scan, all access to those systems is initiated via the LAN address. When displaying a list of registered devices, you have the option of using either the LAN address or the WAN address. This can be useful when the WAN address has been configured but is not yet available or when a registered device is installed remotely and not available on the LAN. The feature is controlled by exactly where you right-click in the list of devices.

If you right-click anywhere other than in the LAN address column, the WAN address is used and the behaviour is otherwise exactly as previously documented. To access the digitiser via its LAN address, right-click in the LAN address column, as shown below:

When you click on the LAN address of an entry, the context menu changes:

Entries for firmware updates, system and GDI configuration and web page access all now use the LAN address rather than the WAN address.

In addition, all options on the Live View sub-menu use the LAN address:

and the calibration page editor is also invoked using the LAN address:

For these techniques to work, the digitiser and PC must be connected to the same LAN.

5.17 Updating Minimus firmware

The firmware of the Minimus is upgradeable. New releases appear regularly – mostly to add new features but, occasionally, to fix problems. Güralp recommends that the Minimus is regularly checked for availability of firmware updates and, when convenient, these updates should be installed.

The procedure below guarantees a straightforward upgrade and prevents any data loss or misconfiguration.

If you have any recorded data that you value, backup all files from the Minimus microSD card:

Once this is complete, to upgrade the Minimus:

5.18 Import / Export an existing configuration

Updating the Minimus’ firmware can, occasionally, cause loss of configuration. We recommend that you export and save the current configuration before proceeding with an upgrade. This operation can be done through Discovery by right-clicking on the digitiser in the list and selecting “System Configuration” from the context menu:

Select "Use configuration from one of the devices". If more than one device is available, select the one from which the configuration should be downloaded. Click the button and browse to a suitable location (on your PC) into which to save the configuration file.

After the firmware update is successfully completed, the previous configuration can be imported, if required, by following the instructions below.

Right-click on the digitiser’s entry in the Discovery list and select "System Configuration" from the context menu. Select the "Use configuration from file" option.

Select the configuration file from where it was saved in the File Explorer and confirm. Use the check-boxes to select the devices to which the configuration should be uploaded and click on the button.

Wait until the process finishes. To apply the new configuration, the unit has to be rebooted: the button can be used to perform the required system restarts.

5.19 Control Centre

Several actions can be taken from within Discovery to control any of the instruments connected to the Minimus as well as the digitiser itself.

This operation can be done by right-clicking on the digitiser’s entry in the list and select “Control Centre” from the context menu. The meanings of the icons are given in the table below.



This tab provides information about the general state of the digitiser, its serial number and IP address, its up-time (time since last boot) and GNSS status.

This button launches a console that allows interactions with the command line of the Minimus. The list of available commands and their respective descriptions can be displayed by entering the command “help”. This should generally only be done on the advice of the Güralp technical support team.

This button is equivalent to the “View Web Page” entry in the context (right-click) menu of the Minimus in the Discovery main window.

This button is equivalent to the “Show on Map” entry in the context (right-click) menu of the Minimus in the Discovery main window.

This button is equivalent to the “Live View” entry in the context (right-click) menu of the Minimus in the Discovery main window.

Hole-lock control for attached Radian instruments. Please refer to Section 5.5 of MAN-RAD-0001 for full details.

This tab allows manual centring of connected analogue and digital (e.g. Radian) instruments. Please refer to Section 7.25 of MAN-RAD-0001 for details about centring Radian instruments.


1. Preliminary Notes 2. System Overview 3. System description 4. Getting started 5. Advanced system configuration 6. GüVü app 7. Advanced troubleshooting 8. Appendix 1 – Instrument/channel names 9. Appendix 2 – Minimus network ports 10. Appendix 3 – Connector pin‑outs 11. Appendix 4 – Dimensions and drawings 12. Appendix 5 – Güralp Discovery installation 13. I.P. address configuration on PC or Laptop 14. Revision History