The PASSCAL Instrument Center (PIC) is the conglomeration of two instrument centers. One that was on the east coast at the Lamont-Doherty Earth Observatory in New York, the other on the west coast at the Geophysics Department of Stanford University. Portable seismic equipment is shipped, developed, and repaired by the instrument center.
There are many different models of equipment. The model that is used is determined by the goals of the experiment. Above is a photograph of two Data Acquisition Systems (DASs), the square boxes, and two external disk drives in the center. The DASs are portable computers that can be programmed to digitize and record the analog signals from seismic sensors at various rates. A typical measurement rate may be 20 samples per second, with increases to 100 samples per second if the unit detects any seismic activity. Some DASs have an internal disk drive for recording the data. External disks may be added if the station is so remote that it may not be "serviced" for an extended period of time, or if the data rate to be used is higher than normal.
This combination of equipment is typically used for experiments where the sensors and DASs will be placed in the field and left unattended for months at a time.
Above is a photograph of the insides of some DASs. There are CPU cards, analog-to-digital (A/D) signal cards, memory cards, oscillator/clock cards, disk drives, and power supply cards.
There are several different models of DASs, but there are more than several different models of sensors. The sensors are the measuring devices that actually feel and measure the ground shaking. They produce electrical signals that are sent to the DASs. The stronger the shaking, the larger the electrical signal. Three sensors used for the detection of earthquakes are pictured above. They are sitting on a Seismic Pier. The pier is basically a large concrete block that provides a stable "quiet" platform for sensor testing. It doesn't work very well, though. People walking by in the lab can easily be detected by the sensors.
All of this equipment doesn't run on love. It needs electricity. The instrument center supplies equipment to power sites whether they be in the desert, or in Antarctica. Short-term experiments may just need batteries, whereas long-term experiments will normally use batteries and solar panels. Wind generators may also be used. Sites typically use two or three 60 watt solar panels.
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