The CD24 is a standard multi-purpose digitiser. The digitizer has 3 24-bit channel with 8 auxiliary channels. The analogue differential inputs connect to the CD24 via the 26 way mil-spec connector.
The features for the CD24 are:
24-bit sigma-delta analogue to digital converter.
Low power: < 1W from 10V–28V DC.
±10V balanced differential input lines.
Lightweight and waterproof.
RS232 output in GCF format.
Multiple user-configurable output rates.
Once it is provided with 10 – 28 V power the CD24 will begin operating automatically digitizing ground movements and either outputting them to your own recording system, or saving them into internal Flash memory. Accurate timing information can be taken from a GPS unit connected to the CD24 through a breakout box. Both breakout box and GPS are normally supplied with the instrument.
State of health information
The CD24 constantly monitors the status of the GPS and timing systems, outputting information in a plain text status stream.
An electronic thermometer also provides regular measurements of the units internal temperature, which are reported in the same stream. The thermometer is calibrated to an accuracy up to ± 0.33 °C, with a linearity of ± 0.5 °C.
The CD24 can be supplied with up to 16 Gb of internal Flash memory for data storage. The amount you need will depend on the length of your experiment and the sampling rates used.
You can download data from the internal storage
over the sensor's standard RS232 data port (compatible with Scream! and other Güralp data modules),
over a fast IEEE.1394 (FireWire) link with optional power,
using an optional “smart” case, over USB from up to five units at once (see Section , page ), or
if fitted, using the Ethernet interface to transfer data over a local area network.
Wireless networking
The CD24 can be fitted with an optional 802.11b (“Wi-Fi”) wireless interface in addition to the Ethernet port. This option allows data flow to be established from autonomous installations with a minimum of setting up.
For temporary deployments, instruments can be buried in shallow pits with only the antenna above ground. You can then contact each station from a wireless-enabled PC running Scream! without disturbing the instrument, including monitoring real-time data and configuring the digitizer.
More permanent arrays also benefit from wireless technology, particularly in remote areas or where the terrain makes long cable runs impractical.
For example, stations might be installed with high-gain antennae directed towards a visible natural feature which is easier to access.
At this location, which can be up to 500 m away, a low-power CMG-DCM data module might act as an access point for the array elements and forward data onto a higher-bandwidth radio link.
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.