• Home
  • Download PDF
  • Order CD-ROM
  • Order in Print
ADJUSTING THE LEVEL TUBE - 14070_114
ADJUSTING THE PLATE BUBBLES - 14070_116

Engineering Aid 1 - Advanced Structural engineering guide book
Page Navigation
  94    95    96    97    98  99  100    101    102    103    104  
Figure  6-3.—Two-peg  test  method. the line of sight is not parallel to the axis of the level tube, then you must adjust the line of sight. The method used for adjustment is known as the  two-peg test  (fig. 6-3). This method requires you to do the following steps: 1. Setup and level the instrument (first setup, fig. 6-3). Drive stake (peg) A about 150 feet away, then drive stake B at the same distance in the opposite direction. 2. Take a rod reading a on stake A and a rod reading b on stake  B. With  the  instrument  exactly  halfway between the two stakes, b-a is the true difference in elevation between the stakes. 3. Move the instrument close to stake  A (second setup, fig. 6-3) so that the eyepiece is within a half inch from  the  rod.  Then,  by  sighting  through  the objective-lens end of the telescope, take a rod reading c on stake A. Next, take a rod reading  d on stake B in the normal manner. If the instrument is in adjustment, d-c will equal b-a. 4. If the instrument is out of adjustment, calculate what the correct rod reading e should be on the farther rod B (e = c + b - a). Set the rod reading  e with a target for accurate reading. Move the horizontal cross hair to the correct reading (on target) by loosening the correct vertical  screw  and  tightening  the  opposite  screw. 5.  Check  the  horizontal  cross  hair  adjustment again.  The  ring  may  have  rotated  during  this  adjustment. 6. Rerun the peg test to check the adjustment. NOTE: The  compensation  for  the  above  maladjust- ment  is  careful  balancing  of  your  backlights  and foresights. Transit Adjustments You  must  be  capable  of  performing  six  commonly performed tests and adjustments of the transit. All tests and  adjustments  of  the  transit  are  made  with  the instrument mounted on its tripod and setup in the shade. You  must  make  these  tests  periodically  and  in  the sequence  in  which  they  are  discussed  in  the  following paragraphs. When one of the tests indicates that an adjustment is necessary, you must make this adjustment and then you must repeat all previous tests before proceeding  with  the  next  test. 6-5







Western Governors University

Privacy Statement
Press Release
Contact

© Copyright Integrated Publishing, Inc.. All Rights Reserved. Design by Strategico.