Wi-Fi débuts at GSL

A 6TD with high-gain antenna.

An on-board serial-to-Ethernet converter allows you to install the 6TD directly onto a wired local area network. Clients using Scream can then connect to the instrument and receive data streams.

For temporary deployments with instruments buried in pits, stations can be contacted from a wireless-enabled PC running Scream! without requiring physical access. Real-time data can be examined and the digitizer configured over the wireless link.

Wireless communication makes data retrieval easy.

For example, stations might be installed with high-gain antennae directed towards a visible natural feature which is easier to access. At this location, a low-power CMG-DCM data module would act as an access point for the array elements and forward data onto a higher-bandwidth radio link.

Wireless links in a semi-permanent array.

In semi-permanent arrays, a wireless-enabled DCM or laptop PC can be set up as a temporary access point for the duration of a site visit.

The CD24 compact digitizer, which provides the digital output features of newer CMG-6TD instruments, is also available as a separate device. Contact Guralp Systems for more information.

Initial testing

The test layout at the GSL factory.

Initial testing and development took place at the Guralp Systems factory. Digitizer modules were placed in locations across the facility and configured to communicate with a standard wireless router in infrastructure mode.

A PC running Scream! connected to each instrument over the wireless network and received data streams.

Using standard, off-the-shelf omnidirectional antennae, reliable continuous data flow was achieved from all instruments. The most distant instrument was located 20 m away through an area of significant interference. Another was placed at a straight-line distance of around 10 m, with signals passing through two exterior walls to reach the access point.

Performance testing

A second test was carried out under field conditions, using battery-powered CMG-6TD sensors equipped with +9dBa omnidirectional antennae.

Testing in field conditions.

The access point seen from the installation at 480 m.

Antennae were mounted around 5 m above ground level on guyed masts at distances up to 480 m from the access point. Line of sight was established for the most distant installation. Installations at 80 and 150 m were obscured by foliage.

Communication was easily established with all three installations using 1/8 of the receiving antenna’s maximum power, and streams were received overnight with no loss of data.

Guralp Systems are now working with research groups to perform detailed performance measurements under true experimental conditions.