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Operator's Guide

Z-secs

N-secs

E-secs

and

X-secs

are the time period over

which to calculate the average for the

, and auxiliary

components respectively. If a component is not considered by
the triggering algorithm (see

TRIGGERS

, above), the value you

specify here will be ignored.

For example,

1 1 2 2 STA

will calculate short-term averages

over 1 s for the

and

components, and over 2 s for the

and

auxiliary components.

If you issue

STA

with only one argument, it is used for all four

components. For example,

5 STA

will calculate averages over 5

s of all components.

LTA

Syntax:

Z-secs

N-secs

E-secs

X-secs

LTA

Sets the length of the “long-term” averaging period in the

STA/LTA

triggering algorithm.

Z-secs

N-secs

E-secs

and

X-secs

are the time period over

which to calculate the average for the

, and auxiliary

components respectively. If a component is not considered by
the triggering algorithm (see

TRIGGERS

, above), the value you

specify here will be ignored.

For example,

15 20 20 20 STA

will calculate long-term

averages over 15 s for the

component, and over 20 s for the

and auxiliary components.

If you issue

STA

with only one argument, it is used for all four

components. For example,

5 STA

will calculate averages over 5

s of all components.

RATIOS

Syntax:

Z-ratio

N-ratio

E-ratio

X-ratio

RATIOS

Sets the ratio of STA to LTA above which a trigger will be
declared in the

STA/LTA

triggering algorithm.

Z-ratio

N-ratio

E-ratio

and

X-ratio

are the time period

over which to calculate the average for the

, and

auxiliary components respectively. If a component is not
considered by the triggering algorithm (see

TRIGGERS

, above),

July 2016

Содержание CMG-DM16R8

Страница 1: ...his manual is proprietary to G ralp Systems Limited and may not be copied or distributed outside the approved recipient s organisation without the approval of G ralp Systems Limited G ralp Systems Lim...

Страница 2: ...the trigger algorithm 21 4 4 Setting the triggered output channels 21 5 Configuring the DM16 22 5 1 Configuring with Scream 22 5 2 Terminal commands 23 5 3 Getting help 25 5 4 General configuration 2...

Страница 3: ...ample rate data streams at user selectable rates Up to 3 streams of data for each component are available at sample rates from 200 samples second down to 2 sps Accurate time synchronisation to externa...

Страница 4: ...ltages to the input stages and the digitizer electronics 1 1 Options G ralp Systems also manufacture a 16 channel DM16 unit the DM16R16 This is a 2U rack mount module containing two 8 channel digitize...

Страница 5: ...series 712 using the cable provided The pinouts for this cable and connector are given at the back of this guide RS 232 Connections Normally the rear Data connector is duplex and the front Monitor con...

Страница 6: ...rear 25 way connector see pinouts attached Terminate unused input ports on the front panel with a 50 BNC terminator cap unless the 25 way rear connector is used for signal inputs into the digitizer I...

Страница 7: ...or the link to SCREAM is simplex GREEN SCREAM is attached and acknowledging blocks the LED blinks momentarily for each block received RED a block s was not acknowledged ExtSync External synchronizatio...

Страница 8: ...upply to the DM16 R8 plug marked Power the DM16 R8 will operate from 10 to 36 V DC At 12 V the DM16 R8 draws 210 220mA or 310 320mA with one GPS2 connected 5 To configure the COM port connected to the...

Страница 9: ...In the Available Streams window the identifier of the digitizer will appear in the left hand frame The data streams will appear in the righthand frame The Stream ID s are six character strings uniquel...

Страница 10: ...e status information coming from the digitizer right click on the status stream from the pop up menu select View A new window Status should open containing text The first blocks will give the boot mes...

Страница 11: ...e this is the only stream with 0 samples per second During boot up the units report their module type firmware revision number the system id and serial number This information is followed by the count...

Страница 12: ...lly backed up status All messages from GPS which involve a change of its status are automatically reported repeated status messages are not shown to avoid unnecessary accumulation of the same informat...

Страница 13: ...this point will be stamped with the time from the internal back up Real Time Clock this is also now reset to this accurate time Re synchronisation will also result in the received data showing a disc...

Страница 14: ...ered i e same temperature the saved control parameters will be appropriate and the system should rapidly switch to the fine control mode 14 Issue C Synchronisation process commenced Internal clock syn...

Страница 15: ...error measurements during the previous minute in time base units nominally 0 5 sec To convert the figures to time divide by 120 60 2 to give micro seconds In a stable temperature environment the syste...

Страница 16: ...ical image was printed from a Guralp plot module to demonstrate the effectivenes of digitizer clock sychronisation and subsequently time stamped data 16 Issue C Offset or phase error between digitiser...

Страница 17: ...igher sample rate during short periods when triggered Parameters controlling the triggering algorithm and controlling the data output once the system is triggered are all selectable by the user permit...

Страница 18: ...an be permitted on any channel Details of the various parameters related to the triggering process are given in the following sections Pre trigger bandpass filtering As the digitizer is normally used...

Страница 19: ...4 0 5 1 8 0 4 1 8 1 1 8 2 0 1 0 9 0 2 0 9 0 5 0 9 As can be seen from the list the choice of required filter will tend to define the set of permissible sample rates required The filter combination is...

Страница 20: ...nd a long time average LTA and the ratio of the two at each sample point is computed STA LTA If this ratio exceeds a user defined threshold then a trigger is declared and the system remains in a trigg...

Страница 21: ...ng the number of false alarms is a matter of experiment In order to capture all of a seismic event some seconds of buffered data from before the trigger is declared are recorded This facility is parti...

Страница 22: ...e block nature of the data format and compression algorithm this time is only approximate Example 20 pre trig post trig defines the amount of time in seconds after the trigger has ceased during which...

Страница 23: ...Operator s Guide July 2016 23...

Страница 24: ...ent channel 2 E W So for example to enable triggering on all three components 001 010 100 111 7 The command is 7 triggers This returns the configuration report Triggering on Data from Tap 2 20s s 70 C...

Страница 25: ...Operator s Guide triggering The configuration report will be Output Triggered Data from Tap 0 200s s 07 Chans 0 1 2 July 2016 25...

Страница 26: ...itizer you want to configure All connected digitizers have an entry in the tree on the left of Scream s main window If the digitizer is transmitting data through a remote server or DCM you may need to...

Страница 27: ...DM16 you can also issue commands to it directly using Scream s terminal mode A terminal window is opened by right clicking on the digitizer s entry in the list and selecting Terminal The digitizer wil...

Страница 28: ...mand in FORTH you must supply the arguments before the command for example 3 SENSOR TYPE In FORTH anything you enter is termed a word New words case insensitive are placed on a stack Some words are kn...

Страница 29: ...tive Sets the system identifier and serial number of the DM16 to values you supply SET ID System Identifier e g ALPHA DM16 Serial e g 1234 00 4507 00 The system identifier you supply may contain up to...

Страница 30: ...internal clock SET CLOCK Enter Date Time YYYY MM DD HH MM SS 2006 02 01 12 53 25 Clock set to 2006 2 1 12 53 27 ok_SBHY The time should be entered in the form year month day hour minute second padding...

Страница 31: ...et the GPS system s advance notification of a leap second and consequently run one second slow until the leap second occurs With SQPATCH enabled the time reported by the digitizer is offset by 1 secon...

Страница 32: ...es sec The DSP software on the DM16 supports up to 7 cascaded filter decimation stages At each stage the sample rate can be decimated by a factor of 2 4 or 5 The ADC within the unit outputs data at 20...

Страница 33: ...s CONTINUOUS Syntax tap components CONTINUOUS Sets which components are output under normal conditions and at which tap s tap is the tap number at which to output the triggered stream You can set whic...

Страница 34: ...RIGGERED Syntax tap components TRIGGERED Selects which component or components will be output when a trigger is generated and at which tap sample rate tap is the tap number at which to output the trig...

Страница 35: ...X secs are the time period over which to calculate the average for the Z N E and auxiliary components respectively If a component is not considered by the triggering algorithm see TRIGGERS above the...

Страница 36: ...ates a filter with a corner at 20 of the Nyquist frequency for tap tap i e 15 of its sample rate filter 5 creates a filter with a corner at 50 of the Nyquist frequency for tap tap i e 25 of its sample...

Страница 37: ...umber of seconds of data to output from before a trigger is declared POST TRIG Syntax time POST TRIG Sets the post trigger recording time time is the number of seconds of data to output after a trigge...

Страница 38: ...d The system is designed around a low power high performance 38 Issue C A B C D E F G H Differential input amplifiers Anti aliasing analogue filters Multiplexor Multiplexor ADC 16 bit linear SAR 56002...

Страница 39: ...ed to UTC To avoid the cost and power consumption of multiple GPS receivers in larger arrays the systems can also be synchronised to a centrally transmitted time reference using a scheme similar to th...

Страница 40: ...ulting in a data output rate of 200 samples sec The following 2 stages can be set individually for decimation factors of 2 4 5 8 and 10 allowing data to be output at lower rates requiring less storage...

Страница 41: ...C power 2 0 V power 7 2 Data connector This is a standard 9 pin D type plug Pin Function 2 RS232 Tx 3 RS232 Rx 5 Isolated Ground 6 RS422 Tx ve 7 RS422 Tx ve 8 RS422 Rx ve 9 RS422 Rx ve 7 3 GPS IN conn...

Страница 42: ...tion 3 GPS Rx 5 Isolated Ground 8 1Hz Reference 7 5 MONITOR connector This is a standard 9 pin D type socket Pin Function 1 VCC 2 RS232 Tx 3 RS232 Rx 4 Bypass Connect to VCC to enable Bypass 5 Isolate...

Страница 43: ...5 Channel C ve 6 Channel D ve 7 Signal Ground 8 Channel E ve 9 Channel F ve 10 Signal Ground 11 Channel G ve 12 Channel H ve 13 Signal Ground 14 Channel A ve 15 Signal Ground 16 Channel B ve 17 Channe...

Страница 44: ...CMG DM16 8 Revision history 2006 11 29 C Updated added revision history 2001 06 01 B Previous release 44 Issue C...

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