TM 5-6635-386-12&P The standard count is taken from Para 1-11. FIELD COUNTS STANDARD COUNT = RATIO 1-24.  DETERMINE DRY WEIGHT Subtract  the  moisture  in  PCF  from  wet  weight  for  each density depth to obtain a dry weight.  The dry weight (DA Form   5448-R)   is   then   used   for   the   determination   of Percent Compaction and Moisture (See Fig 1-10). 1-25.  COMPUTE PERCENT COMPACTION The tester has now provided the actual, in place density and   moisture   obtained   during   compaction   of   the   soil Whether this is good enough for the project is not known until   we   compare   this   in   place   density   with   the   soil maximum density produced from a laboratory sample of the   soil   being   tested   (found   in   a   Corps   of   Engineers handbook or determined by actual laboratory tests).  This is the "Proctor" value or soil maximum density.  To obtain a Percent Compaction (DA Form 5448-R) we  divide  the dry  density  by  the  Proctor  value  which  is  assumed  to equal 130 PCF.  (See Fig. 1-11). DRY WEIGHT OPTIMUM = % SOIL MAXIMUM DENSITY COMPACTION 1-26.  COMPUTE PERCENT MOISTURE Percent  moisture  is  expressed  as  a  percent  of  the  dry weight   in   soil   testing.      Therefore   we   must   divide   the moisture   in   PCF   by   the   dry   weight   in   PCF   to   obtain percent moisture dry, DA Form 5448-R (See Fig 1-12). H20 IN PCF DRYWIEGHT = % MOISTURE DRY 1-27.  COMPLETION OF TEST Upon   completion   of   the   testing   and   before   tester   is placed in carrying case, remove battery pack and store it separately.    It  is  not  necessary  to  turn  the  tester  off  or perform  other  operations.    Also   insure   that   the   tester handle  is  in  safe  position  prior  to  placing  the  tester  into storage case. 1-28.  CALIBRATION CHARTS CPN  calibration  curves  or  charts  are  determined  from tests taken on CPN calibration standards. CPN  uses  a  variety  of  standards  for  gauge  calibration including natural standards and artificial (metal) standards.  Unfortunately, there is no "National Bureau of Standards"  in  the  nuclear  soil  gauging  industry.    Each manufacturer does his best to provide an accurate set of standards and he checks these  standards  against  other standards wherever possible.  The major manufacturers generally agree quite closely on their standards although some    disagreement    may    exist    here    and    there    with standards of users who have made them themselves. If the chart produces results suspected of being in error (conflicts  with  field  results  of  other  testers  or  of  other compaction measurements) do the following: Check operation of tester.  (See Para 1-7). Check accuracy of other testers. Retest a prior site that was correct 1-29.  MOISTURE MEASUREMENT ERRORS The  moisture  channel  is  actually  a  "hydrogen  analyzer". It    responds    to    moderated    neutrons,    the    moderation largely a function of neutron collisions with hydrogen and only   incidentally   a   function   of   collision   with   the   large nuclei of other atoms. Thus,  any  source  of  hydrogen  will  result  in  moderated neutrons     and     the     tester     will     attempt     to     respond accordingly. This   can   be   used    to    our    advantage    in    deliberately measuring  asphalt  content  where  the  only hydrogen that    we    would    expect    to    "see"    would    be    from    the hydrocarbons in the AC and not from moisture. However, the hydrogen analyzer aspect of the tester can also   be   to   our   detriment   if   the   soil   we   are   trying   to measure    has    hydrogen    from    other    than    free    water around the mineral particles. 1-18