﻿NOV. 
  4, 
  1922 
  zahn: 
  recording 
  electric 
  contact 
  415 
  

  

  The 
  following 
  is 
  an 
  application 
  of 
  this 
  electron 
  tube 
  recorder. 
  In 
  

   the 
  Automotive 
  Power 
  Plant 
  Section 
  of 
  the 
  Bureau 
  of 
  Standards 
  a 
  

   method 
  has 
  been 
  devised 
  to 
  record 
  automatically 
  the 
  pressure-volume 
  

   curve 
  for 
  a 
  gas 
  engine 
  c>cle.- 
  A 
  mechanical 
  arrangement 
  was 
  worked 
  

   out 
  which 
  for 
  any 
  given 
  pressure 
  makes 
  an 
  electric 
  contact 
  con- 
  

   tinuously 
  during 
  the 
  time 
  of 
  the 
  cycle 
  when 
  the 
  pressure 
  in 
  the 
  engine 
  

   cylinder 
  is 
  greater 
  than 
  or 
  equal 
  to 
  this 
  given 
  pressure. 
  Thus 
  the 
  

   pressure 
  in 
  the 
  engine 
  cylinder 
  is 
  equal 
  to 
  this 
  given 
  pressure 
  at 
  times 
  

   corresponding 
  to 
  the 
  makes 
  and 
  the 
  breaks 
  of 
  electric 
  contact, 
  and 
  these 
  

   times 
  correspond 
  to 
  points 
  on 
  the 
  curve 
  whose 
  ordinates 
  are 
  equal 
  to 
  

   the 
  given 
  pressure. 
  It 
  was 
  attempted 
  to 
  register 
  this 
  time 
  of 
  contact 
  

   by 
  low-frequency 
  sparks. 
  A 
  drum 
  covered 
  with 
  carbon 
  paper 
  was 
  to 
  

   be 
  rotated 
  in 
  synchronism 
  with 
  the 
  engine, 
  and 
  for 
  any 
  given 
  pressure 
  

   the 
  time 
  of 
  sparking 
  would 
  be 
  registered 
  on 
  the 
  paper. 
  For 
  the 
  differ- 
  

   ent 
  pressures 
  parallel 
  lines 
  would 
  be 
  registered, 
  all 
  of 
  which 
  together 
  

   would 
  give 
  the 
  pressure 
  diagram 
  in 
  the 
  form 
  of 
  an 
  area 
  of 
  sparks. 
  The 
  

  

  Fig. 
  3. 
  Carbon 
  paper 
  record 
  of 
  spark 
  passing 
  when 
  chopper 
  contact 
  is 
  closed. 
  

  

  difficulties 
  found 
  in 
  trying 
  to 
  use 
  low-frequency 
  methods 
  should 
  be 
  

   obviated 
  by 
  applying 
  the 
  device 
  described 
  in 
  this 
  paper. 
  

  

  The 
  time 
  of 
  duration 
  of 
  the 
  radio-frequency 
  spark 
  in 
  the 
  experi- 
  

   ments 
  described 
  in 
  the 
  beginning 
  of 
  this 
  paper 
  is 
  actually 
  registered 
  

   as 
  a 
  series 
  of 
  dots 
  about 
  a 
  millimeter 
  apart 
  and 
  the 
  equality 
  of 
  time 
  

   interval 
  of 
  contact 
  and 
  open 
  circuit 
  is 
  registered 
  on 
  the 
  carbon 
  paper 
  to 
  

   an 
  accuracy 
  corresponding 
  approximately 
  to 
  the 
  distance 
  between 
  the 
  

   dots 
  just 
  mentioned. 
  It 
  is 
  believed 
  that 
  if 
  the 
  length 
  of 
  spark 
  gap 
  is 
  

   reduced, 
  the 
  accuracy 
  of 
  the 
  production 
  of 
  equal 
  intervals 
  can 
  be 
  con- 
  

   siderably 
  increased. 
  The 
  fact 
  that 
  a 
  series 
  of 
  dots 
  is 
  obtained 
  in- 
  

   stead 
  of 
  a 
  continuous 
  cut 
  in 
  the 
  paper 
  is 
  probably 
  due 
  to 
  differences 
  in 
  

   conductivity 
  of 
  the 
  paper 
  at 
  different 
  points 
  or 
  to 
  an 
  effect 
  on 
  the 
  tube 
  

   generator 
  due 
  to 
  the 
  passing 
  of 
  the 
  spark 
  from 
  the 
  coil 
  L3. 
  The 
  fre- 
  

   quency 
  of 
  these 
  dots 
  is 
  about 
  one 
  fiftieth 
  that 
  of 
  the 
  radio-frequency. 
  

  

  2 
  H. 
  C. 
  Dickinson 
  and 
  F. 
  B. 
  Newell, 
  "A 
  High-Speed 
  Engine 
  Pressure 
  Indicator 
  of 
  the 
  

   Balanced 
  Diaphragm 
  Type," 
  Report 
  No. 
  107 
  of 
  the 
  National 
  Advisory 
  Committee 
  for 
  

   Aeronautics, 
  Washington, 
  1921. 
  Government 
  Printing 
  Office. 
  

  

  