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Earthworm Overview
Earthworm is a public domain collection of programs for acquiring,
processing, and saving earthquake data that has become popular with
many geophysicists. Symmetric Research modules work with versions of
Earthworm running under Windows and Linux.
Earthworm is composed of many separate programs, called modules, which
read and write data from shared memory regions known as rings. Some
modules send data from one ring to another over the network. This
allows Earthworm to run in a distributed fashion using several
different computers.
USBxCH/PARxCH and Earthworm
Any of our USBxCH or PARxCH 24 bit A/D's can be used to supply
acquired data to an Earthworm system by running the SrUsb2Ew or
SrPar2Ew (formerly called SrParxchEwSend) modules respectively. Once
Earthworm is up and running, Sr2Ew modules start acquisition on the SR
A/Ds and send the acquired waveform data to the WAVE_RING specified in
the usual Earthworm style .d configuration file. They also send
regular heartbeat messages.
In order to run either Sr2Ew module, you will need a working Earthworm
system, a USBxCH or PARxCH A/D system, and the device driver software
that comes with the system and is also available free from our
download page. The four channel USB4CH and 1, 4, and 8 channel
versions of the PARxCH A/D's are available. With Earthworm, sampling
rates up to 1000 Hz are allowed as long as the rest of your Earthworm
processing can keep up.
If accurate timing information is important for your application, you
will also want to use a GPS antenna or our PARGPS timing unit for
timestamping the acquired data. The time stamping is done in the
hardware and does NOT require feeding PPS into an analog channel. For
the PAR1CH and PAR4CH, typical time stamp accuracy is 10us, while the
USB4CH and PAR8CH deliver an improved accuracy of 800 ns.
Earthworm systems are well suited to distributed networks. When
setting up a remote node or field station, you may want to consider
pairing an SR A/D with a commercially available
Mini ITX System.
These compact, low priced PC's are easy to use and typically have low
power requirements too.
The Sr2Ew modules will work for Windows and Linux since those are the
operating systems for which A/D device drivers are available. There
is no support for Solaris.
General questions about Earthworm are probably best answered by the
Earthworm User's discussion group. But, if you have specific
questions about SrUsb2Ew or SrPar2Ew and their configuration parameters,
please let us know at info@symres.com.
Earthworm Links
Download SrUsb2Ew and SrPar2Ew
The Sr2Ew Earthworm modules are included in the standard Earthworm
distribution starting with version 7.4 (version 6.3 for SrParxchEwSend).
They are also included in the USBxCH and PARxCH with PARGPS system software
which are available free from our
Downloads page.
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