Components of a typical PNSN Strong Motion Station:

Internet-interface

Data telemetry for most PNSN Strong Motion stations will be over an IP computer network using TCP. A terminal server provides the interface between the seismograph and the Internet, acting as a serial-to-Ethernet converter.

The terminal server receives data packets from the seismograph on a RS-232 port. It "wraps" the data in TCP/IP and sends the data out on a 10Base-T port. The seismograph sends data continuously to the terminal server which buffers the data and resends it as necessary. Data rates are around 1,500 bytes per second which includes both data and packet headers. Data latency is on the order of 1.5 seconds and thus Internet connection interuptions of more than this may cause some data loss. We are working on internal buffering schemes to increase tolerable latency durations to minutes.

The terminal server should be assigned an IP address prior to station installation. If a firewall exists at the site it will be necessary to configure the firewall for UW access to a specific IP address and port number. Two different ports are used, one for data and one for the command interface to the terminal server.

The terminal server uses a RJ-45 type 10Base-T Ethernet connection.

The model used by the PNSN is the MSS-100 Universal Thin Server manufactured by Lantronix.

The terminal server is located in the Guralp power supply housing. An internal battery will power the system for about a day in the event of the loss of AC power. The power supply housing has 3 external connections:

• Ethernet 10/100 Base-T
• AC power
• Serial connection to sensor

 

Updated August 7, 2002