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Please review the manual from EAI giving all details on the seismometer set-up and voltage checks. The following is the typical seismometer installation.
- Remove the seismometer from its protective wrapping. Retrieve the two black cables packaged along with it. One cable has a 5 prong connector with several exposed wires on the opposite end. The other cable has a 9 prong connector on one end and a power supply that plugs into a standard 120 volt AC wall outlet on the opposite end. Place the seismometer on the predetermined site.
- Attach the cable with the 5 prong connector to the seismometer.
- Attach the cable with the 9 prong connector to the seismometer but do not plug the other end into a wall outlet at this time.
- Level the seismometer. On top of the instrument is a "bullseye" bubble type level. Beneath the seismometer are three legs, each consisting of a bolt and nut. Use a crescent wrench or 3/8 inch open end wrench to loosen the nuts (the nuts may be a bit snug, so be gentle but firm). Turn the legs to center the level bubble into the bullseye. Leveling the seismometer is vitally important and great care should be taken to center the bubble in the bullseye precisely.
- Unlock the beam, or in other words, release the protective clamps within the seismometer which protect it during transport. Once the beam is unlocked, it is important that the seismometer not be moved as this can damage the instrument. Notice the plastic, white screws on either end of the seismometer. There will be [2] on one end and [1] on the other.
Beginning at the end with [2] screws, slowly turn them, simultaneously, in a counterclockwise direction. Look from directly overhead at the screws and watch as they back away from the gray bar (beam) which is perpendicular to the screws. Slowly turn the screws until there is ¼ inch gap between the screws and the beam.
Follow the same procedure on the side with [1] screw. As the screw backs out, there will be a point at which you feel the beam release. There will be a slight bounce as the beam becomes free. Again, back the screw out until there is a ¼ inch gap between it and the beam.
- Recheck the level of the seismometer. Carefully adjust if necessary.
- Before calibrating the seismometer voltage connect the instrument to the computer. Follow the instructions on Installing the A-to-D Board and Installing the Connector Block
- After the seismometer is connected to the computer power it up by plugging it into a nearby wall outlet.
- Calibrate the seismometer voltage with the LCD digital multimeter. Locate the seismometer cable that connects to the connector block. Turn on the digital multimeter and make sure it is set to read DC Volts. Press the black (- Com) multimeter probe to the exposed end of the black wire running out of the seismometer cable. Simultaneously, press the red (+) probe to the solid blue wire from the seismometer cable (click to view diagram). The multimeter should read a positive voltage. The target value is 1.6 Volts. The seismometer voltage must register within ±0.1 Volts of the target value.
If the seismometer is not within the target range an adjustment is required. Located the small allen wrench that came with the seismometer (found in a small white envelope). Located on the side of the instrument which has [2] white screws, near the top, there is a small hole containing a hex screw. Place the wrench in that hole and slowly turn to adjust the voltage. Turning clockwise will raise the voltage while counterclockwise lowers it. The seismometer is very sensitive, a small adjustment can change the voltage drastically.
After the voltage calibration is complete the seismometer should be producing a voltage between the +Out and ground wires that is proportional to ground velocity.
Last update March 11, 2003
Ohio Seismic Network http://www.dnr.state.oh.us/OhioSeis
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