Chapter 2. Introduction

2.1 Equipment Overview

The Guralp Systems CMG-CD24R6EAM is an acquisition module providing a guaranteed 100ms low-latency Ethernet output with full system redundancy.

Inside each acquisition module are a pair of CMG-CD24 digitisers, a Lantronix Wi-port NR Ethernet module and a CMG-EAM communication and control module.

The CMG-CD24 is an analogue to digital converter that receives signals from connected seismometers and other devices and feeds the digital output to both the Lantronix Wi-port NR and a CMG-EAM modules. The Lantronix Wi-port NR provides a guaranteed 100ms low latency Ethernet output and the EAM provides Ethernet and serial outputs.

GPS timing is used throughout, there is an internal mass storage device and protection is provided through GPS and Network surge protectors.

On the front of the acquisition module is an LCD display which cycles though a series of status messages such as the IP address and GPS status.

The system architecture is given in section 2.3.

2.2 Ports

2.2.1 External Ports

There are 8 ports on the back of the acquisition module. These are described below.

2.2.1.1 Sensor A and Sensor B

Two 26-pin connectors that provide power to the instruments and accept analogue signals from connected sensors.

2.2.1.2 ETHERNET

The two 6-pin 100BASE-TX Ethernet ports support connection to a hub, switch or router. The low-latency port connects to the Lantronix WiPort NR device and the other connects to the CMG-EAM.

2.2.1.3 GPIO

The 12-pin GPIO (General Purpose Input/Output) port fulfils three functions: it provides a serial console to the EAM, which can be used for monitoring, configuration and control; it provides USB access from a PC or laptop to the internal mass storage device for data collection and it provides a number of tri-state lines which can be used to control or monitor external equipment. One application is as tamper detection lines, which can be connected to external switches and monitors as part of a secure installation.

2.2.1.4 USB

The 6-pin USB port allows connection of an external USB storage device for data collection. It is also possible to perform firmware upgrades using this port in situations where internet access is not available.

2.2.1.5 GPS

The 10-pin GPS port connects to a Guralp Systems GPS receiver which acts as a timing source for time-stamping seismic data.

2.2.1.6 PWR/DATA

The 10-pin Power/Data Out port is the power input and general-purpose serial port. It is a command line terminal running at 115,200 Baud in the default configuration but it can also be used for GCF output, PPP network connections, inbound GCF (from a digital instrument, for example), NMEA functions, TCP serial conversion, a modem answering service or as a recorder to store and forward data from any instrument with a serial output.

2.2.2 Internal Ports

There are two internal ports that can be accessed by removing the top cover from the acquisition module. These are described below.

2.2.2.1 USB

The internal USB connector allows for the installation of a suitable mass storage device. An 8Gb mass storage device is supplied as standard and can be upgraded if required.

2.2.2.2 D-connector

The 9-pin D connector provides RS232 access to the Lantronix WiPort NR device for advanced configuration (see Appendix C on page 23).

2.3 System Architecture

2.3.1 Acquisition module

The primary system architecture of the acquisition module is given in the figure below. Not all input and output ports are shown, these are listed in section 2.2.

The A and B inputs are analogue signals from attached seismometers as shown in the next section.

Configuration and control of the Lantronix Wi-port NR and a CMG-EAM modules is carried out via the web interfaces as detailed in section 3.

Configuration and control of the digitisers is carried out via the EAM web interface. The EAM also provides power to the CD24 digitisers.

For more information on the internal devices refer to the following manuals available from the Guralp Systems website: www.guralp.com

MAN-EAM-0003 for the CMG-EAM

MAN-C24-0001 for the CD24

For more information on the Lantronix WiPort NR refer to the manufacturers documentation:

www.lantronix.com/pdf/WiPort-NR_UG.pdf

2.3.2 Example sensor station

An example of a complete sensor station is shown in the figure below. The dual outputs from each CMG-5TC sensor are split as shown, each feeding an acquisition module. In this arrangement there is a duplex system with full redundancy from the sensor to the network outputs.

The supplied instruments are standard CMG-5TC accelerometers that have been configured so that all outputs are low gain.

For more information on the instruments refer to the CMG-5TC manual (MAN-050-0004) available from the Guralp Systems website: www.guralp.com.