Lacoste & Romberg Gravimeter Instructions

1. Remove from case and connect power source. Gravimeter requires two hours to reach operating temperature.

2. To take a reading, place gravimeter on its circular plate and level using the black leveling knobs. Turn on light switch.
   • Turn damping knob counterclockwise to its furthest extent. DO NOT MOVE GRAVIMETER!
   • Turn dial to the left to move galvanometer needle left; turn dial right to move needle right. Adjust dial until needle is in 12 o'clock position.
   • Peer through the eyepiece and locate the beam. Adjust dial so the left side of beam matches the left side of the 2.7 reading line.
   • Record the number in the counter. There is a decimal place before the last digit. The last digit on the counter should match the last digit on the dial. Estimate one more digit from the dial.

     Example: The counter number is 37212. The dial number is 2.l. The meter reading is 3721.21.

   • The meter reading in milligals is obtained by finding the highest tabled value lower than the new reading. Record the value of the table value in milligals. Subtract the table value from the meter reading and multiply this difference by the tabled interval factor to convert this difference to milligals. Add the tabled milligal value to the calculated value.

     For a calibration table for UNR's meter G-509, see this GIF.

     Example:

     Meter reading: 3721.21
     Highest tabled value: 3700
     Difference: 21.21
     Interval factor: 1.02428
     Difference x Interval Factor. 21.72 mGal
     Highest tabled value in milligals: 3791.57 mGal
     Sum: 3813.29 mGal

3. After taking a reading, BE SURE TO TURN DAMPING KNOB CLOCKWISE TO ITS FURTHEST EXTENT before moving. Turn off light. Return instrument to case.