TM 1-1500-204-23-4 the barometric dial is immaterial.  The vibrator must be energized   throughout   this   test.      Beginning   with   the barometric  pressure  at  31.018  inches  of  mercury  the altimeter  shall  be  subjected  to  successively  decreasing then   increasing   pressures   corresponding   to   altitudes specified  in  table  4-6.    The  reduction  m  pressure  shall be  made  at  a  rate  not  in  excess  of  10,000  feet  per minute to within approximately 300 feet of the test point. The test point shall be approached at a rate compatible with Table 4-5.  Pressure Altitude Difference (Three Pointer) Pressure Altitude (inches of difference mercury (Hg)) (feet) 28.10 .......................................... -1727 28.50 .......................................... -1340 29.00 .......................................... -863 29.50 .......................................... -392 29.92 .......................................... 0 30.50 .......................................... +531 30.90 .......................................... +893 30.99 .......................................... +974 Table 4-6.  Scale Error (Counter Drum Pointer) Altitude Equivalent pressure Tolerance (feet) Inches of mercury-Hg) ±(feet) -1000 31.018 ±30 0 29.921 ±30 500 29.385 ±35 1000 28.856 ±35 2000 27.821 ±40 3000 26.817 ±45 5000 24.896 ±50 8000 22.224 ±60 10000 20.577 ±65 12000 19.029 ±70 15000 16.886 ±80 18000 14.942 ±90 20000 13.750 ±95 25000 11.103 ±105 30000 8.885 ±115 35000 7.041 ±125 38000 6.097 ±140 40000 5.538 ±140 45000 4.355 +185 50000 3.425 ±500 the  test  equipment.    The  altimeter  shall  be  kept  at  the pressure  corresponding  each  test  point  for  at  least  one minute, but not more than five minutes before a reading is taken.  The error at all test points must not exceed the tolerance specified in table 4-6. 2 Hysteresis test.    The  hysteresis test  shall  begin  not  more  than  15  minutes  after  initial exposure of the altimeter to the pressure corresponding to  the  upper  limit  of  the  scale  error  test  prescribed  in paragraph 1.  While the altimeter is at this pressure, the hysteresis  test  shall  commence  with  vibrator  operative. Pressure   shall   be   increased   at   a   rate   simulating   a descent in altitude at the rate of 5,000 to 20,000 feet per minute until within 3,000 feet of the first test point, table 4-7.  The test point shall then be approached at a rate of approximately)  3,000  feet  per  minute.    The  altimeter shall  be  kept  at  this  pressure  for  at  least  1  minute,  but not  more  than  15  minutes,  before  the  test  reading  is taken.    After  the  reading  has  been  taken,  the  pressure shall   be   increased   further,   in   the   same   manner   as before,  until  the  pressure  corresponding  to  the  second test  point  table  4-7,  is  reached.    The  altimeter  shall  be kept at this pressure for at least 1 minute, but not more that 10 minutes, before the test reading is taken.  When the   reading   has   been   taken,   the   pressure   shall   be increased  further,  in  the  same  manner  as  before,  until third test point table 4-7 is reached.  The reading of the altimeter at either of the three test points shall not differ by  more  than  the  tolerance  specified  in  table  4-7  from the    reading    of    the    altimeter    for    the    corresponding altitude recorded during the scale error test prescribed in paragraph 1. 3 After-effect  test.    With  vibrator operative    and    not    more    than    five    minutes    after completion of the hysteresis test prescribed in paragraph   2   the   altimeter   reading   (corrected   for   any change  in  atmospheric  pressure)  shall  not  differ  from the original atmospheric pressure reading by more than the tolerance specified in table 4-7. Table 4-7.  Test Tolerances (Counter Drum Pointer) Tolerance Test (feet) Case LeakTest ...................................... 100 Hysteresis Test: First Test Point (25,000)........................ 60 Second Test Point (20,000) ................... 60 Third Test Point (0) ............................... 30 After-Effect Test.................................... 30 Change 3   4-18