﻿on 
  the 
  Plug 
  Permeameter. 
  

  

  Table 
  II. 
  

   Relation 
  of 
  H 
  to 
  H'. 
  

  

  135 
  

  

  H. 
  

  

  Mean 
  H' 
  

  

  Mean 
  H' 
  

  

  Mean 
  H' 
  

  

  Mean 
  H' 
  

  

  Mean. 
  

  

  for 
  O.C.I. 
  

  

  for 
  S.C.I. 
  

  

  for 
  W.L 
  

  

  for 
  M.S. 
  

  

  

  

  

  

  

  

  

  

  

  

  

  

  5 
  

  

  8'5 
  

  

  9-7 
  

  

  8-5 
  

  

  8-0 
  

  

  8-7 
  

  

  10 
  

  

  17-2 
  

  

  19-2 
  

  

  18-75 
  

  

  18-5 
  

  

  18-4 
  

  

  15 
  

  

  26-2 
  

  

  29-4 
  

  

  28-2 
  

  

  290 
  

  

  28-2 
  

  

  20 
  

  

  340 
  

  

  39-0 
  

  

  35-7 
  

  

  377 
  

  

  36-6 
  

  

  25 
  

  

  42-2 
  

  

  47-7 
  

  

  42-2 
  

  

  46-5 
  

  

  44-7 
  

  

  30 
  

  

  49-5 
  

  

  56-0 
  

  

  48 
  

  

  54-2 
  

  

  51-5 
  

  

  35 
  

  

  57'0 
  

  

  65-25 
  

  

  540 
  

  

  61-0 
  

  

  59-3 
  

  

  40 
  

  

  63-5 
  

  

  73-75 
  

  

  60-5 
  

  

  66-5 
  

  

  660 
  

  

  45 
  

  

  69-5 
  

  

  81-75 
  

  

  64-5 
  

  

  72-2 
  

  

  71-9 
  

  

  50 
  

  

  76-5 
  

  

  90-75 
  

  

  69-7 
  

  

  775 
  

  

  78-5 
  

  

  55 
  

  

  83-5 
  

  

  98-25 
  

  

  750 
  

  

  82-0 
  

  

  84-7 
  

  

  60 
  

  

  900 
  

  

  1060 
  

  

  79-5 
  

  

  88-5 
  

  

  910 
  

  

  65 
  

  

  96-5 
  

  

  114-0 
  

  

  83-7 
  

  

  93-2 
  

  

  96-9 
  

  

  70 
  

  

  103-0 
  

  

  121-5 
  

  

  89-0 
  

  

  97-5 
  

  

  102-8 
  

  

  75 
  

  

  109-2 
  

  

  1290 
  

  

  94-2 
  

  

  102 
  2 
  

  

  108-6 
  

  

  80 
  

  

  115-0 
  

  

  135-7 
  

  

  99-0 
  

  

  108-5 
  

  

  114-6 
  

  

  In 
  order 
  to 
  show 
  the 
  result 
  o£ 
  correcting 
  the 
  indications 
  of 
  

   the 
  instrument, 
  the 
  curves 
  figs. 
  2-9 
  have 
  points 
  marked 
  by 
  

   crosses, 
  in 
  which 
  the 
  readings 
  of 
  the 
  plug-permeameter 
  are 
  

   shifted 
  backwards 
  along 
  the 
  H 
  axis 
  by 
  amounts 
  corresponding 
  

   to 
  the 
  mean 
  curve 
  in 
  fig. 
  10. 
  The 
  agreement 
  with 
  the 
  ring- 
  

   tests 
  then 
  becomes 
  fairly 
  good. 
  Fig. 
  11, 
  PI. 
  III., 
  shows 
  readings 
  

   taken 
  by 
  one 
  of 
  the 
  portable 
  testing 
  sets, 
  in 
  which 
  the 
  H 
  scale 
  

   has 
  been 
  marked 
  off 
  in 
  this 
  way. 
  The 
  curves 
  are 
  those 
  given 
  

   by 
  the 
  ring 
  method, 
  while 
  the 
  points 
  are 
  taken 
  by 
  the 
  testing 
  

   set. 
  The 
  agreement 
  is 
  as 
  good 
  as 
  in 
  most 
  of 
  the 
  recognized 
  

   permeameters. 
  

  

  Fig. 
  12, 
  PI. 
  III., 
  shows 
  two 
  curves 
  taken 
  by 
  the 
  plug 
  perme- 
  

   ameter 
  : 
  one 
  on 
  a 
  cast-steel 
  pole-piece 
  for 
  a 
  large 
  generator, 
  

   which 
  was 
  sent 
  us 
  by 
  the 
  dynamo-builders 
  under 
  the 
  impres- 
  

   sion 
  that 
  it 
  was 
  of 
  poor 
  magnetic 
  quality. 
  The 
  test 
  shows 
  

   the 
  permeability 
  to 
  be 
  very 
  good. 
  The 
  other 
  curve 
  is 
  for 
  

   another 
  specimen 
  of 
  steel, 
  and 
  indicates 
  the 
  remarkable 
  

   variations 
  of 
  quality 
  which 
  are 
  found 
  in 
  practice. 
  

  

  It 
  should 
  be 
  mentioned 
  that 
  when 
  the 
  plug 
  used 
  in 
  these 
  

   tests 
  was 
  replaced 
  by 
  a 
  second 
  one, 
  the 
  results 
  agreed 
  within 
  

   an 
  accuracy 
  of 
  1J 
  per 
  cent. 
  

  

  The 
  general 
  conclusion 
  to 
  be 
  drawn 
  from 
  these 
  experiments 
  

   is 
  that 
  the 
  plug 
  permeameter, 
  in 
  reasonably 
  careful 
  hands, 
  

   gives 
  as 
  good 
  results 
  as 
  any 
  other 
  method 
  of 
  iron 
  testing, 
  so 
  

   far 
  as 
  permeability 
  tests 
  are 
  concerned. 
  In 
  a 
  recent 
  paper 
  

  

  