Minicom Advanced Systems CMG-DCM manual General digitizer settings

CMG-DCM

alter the settings on the digitizer to reflect your choices; this done, you should see the message New configuration successfully saved to attached instrument.

If the DCM is connected to a PC running Gü ralp Systems' Scream! software, you can also configure the digitizers from within Scream!. See the User Guide for your digitizer model for more details.

General digitizer settings

Baud rate : The speed at which the digitizer will communicate with the DCM, in bytes per second. This must match the baud rate the DCM is using for the serial port linked to this digitizer. The DCM's baud rates can be altered on the various Serial port configuration pages: see Section 4.3, “Serial port configuration”.

You should ensure that the baud rate is high enough to allow all the data to be transmitted at the rates you have chosen. As an example, for three streams transmitting at 100 Hz, a rate of 9600 baud is usually sufficient. Modern modems can normally operate at rates up to 57600 baud (~56 kbits/s), although the telephone or transmission lines may not support such a high rate. The same is true of radio telemetry links.

System ID and serial number : Together, these two fields uniquely identify data originating from a particular instrument. Every data or status block sent by the digitizer will contain them as the first two 32-bit fields in the header, each encoded as a sequence of 6 base-36 numbers representing alphanumeric characters. On delivery of the digitizer from the factory, the system ID is set to the Gü ralp Systems works number, and the serial number is unique for that digitizer (unless shared with an attached seismometer). You may reset these values to any combination of up to 6 letters and numbers. For example, you may wish to set the system ID to a more easily-recognised value, such as an abbreviation of your institution's name.

Sensor type : If the sensor attached to the digitizer is a Gü ralp velocity sensor, useful seismometer functions (such as sensor locking, centering, and calibration) may be controlled through the digitizer and DCM. In order to be able to do this, and to know which functions to make available, the digitizer must be set up with the correct sensor type: one of CMG-40T,CMG-3ESP,or CMG-3T. The sensor's type will be printed on its casing. If you have taken delivery of a DCM already bonded to a sensor and digitizer, this field will have been set for you at the factory, and should not be altered.

Timing source : The digitizer needs to be able to time-stamp accurately all data that passes through it. It can set its clock either by receiving time signals from the GPS satellite network using an attached Garmin GPS unit, or by taking time information from a central site via the DCM (stream sync mode). In stream sync mode, the digitizer expects to receive GCF packets from the central timing

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