TM 5-3895-374-24-2 INSTALLATION 1. LOCATION:        Select    a    location    where    the temperature of the unit will be between 20F and 120F.  Distance from the receiver is limited only by     total     loop     resistance. See "Electrical Connections." The tubing feeding pressure to the instrument   can   be   run   practically   any   length required but long lengths  will  increase  response time   slightly.      Avoid   surfaces   with   excessive vibration. 2. POSITION:  The Model 604-0 must be mounted and operated only in a vertical position due to its sensitivity  to  gravitational  forces.    Higher  range models will perform properly at other angles, but they must be spanned and zeroed in the position in  which  they  will  be  used.    The  minimum  and maximum  ranges  possible  may  shift  depending upon degree of tilt. 3. PRESSURE    CONNECTIONS:        Two    barbed connectors  are  provided  for  use  with  3/16"  I.D. vinyl    or    rubber    tubing.        Attach    tubing    from positive  pressure  source  to  HI  port.    Leave  LO port   vented.   For   negative   (vacuum)   pressure, connect  to  LO  port  and  leave  HI  port  vented. For  differential  pressures,  connect  the  higher  to HI port and lower to LO port. 4. MOUNTING:    Attach  the  Series  604  transmitter to a vertical surface using the 1"--#10 pan head sheet   metal   screws   provided.   Mounting   holes are located  in  upper  left  and  lower  right  comers of case. ELECTRICAL CONNECTIONS CAUTION:      DO   NOT   EXCEED   SPECIFIED   SUPPLY VOLTAGE   RATINGS.      PERMANENT   DAMAGE   NOT COVERED   BY   WARRANTY   WILL   RESULT.      THIS UNIT IS NOT DESIGNED FOR AC VOLTAGE OPERATION. Electrical  connections  to  the  Series  604  transmitter  are made  inside  the  enclosure  on  the  left  side  of  the  unit. Remove    the    cover,    feed    stripped    and    tinned    leads through  the  bottom  holes  and  connect  to  terminal  block screws marked + and -.  Refer to Figure A for locations of  terminal  block,  span  and  zero  adjust  potentiometers. See Figure B for schematic diagram. FIGURE A An external power supply delivering 12.3 to 35 VDC with a  minimum  current  capability  of  20  milliamps  must  be used  to  power  the  control  loop  in  which  the  Series  604 transmitter is connected.  Refer to Fig.  B for connection of the power supply, transmitter and receiver.  The range of   appropriate   receiver   load   resistances   (R,)   for   the power  supply  voltage  available  is  given  by  the  formula and   graph   in   Fig.      C.      Shielded   two   wire   cable   is recommended   for   control   loop   wiring   and   the   cable shielding may be grounded if desired. Note also that the receiver   may   be   connected   in   either   the   negative   or positive  side  of  the  loop,  whichever  is  most  convenient. Should     polarity     of     the     transmitter     or     receiver     be inadvertently reversed, the loop will not function properly but no damage will be done to the transmitter. FIGURE B The  Series  604  transmitters  can  be  used  with  receivers requiring   1-5   volt   input   rather   than   4-20   mA.      If   the receiver  requires  a  1-5  volt  input,  insert  a  250  ohm,  1/2 watt resistor in series with the current loop but in parallel with   the   receiver   input.      Referring   to   Figure   B,   RL becomes  the  250  ohm  resistor  and  points  X  and  Y  are connected to the receiver input, point Y being positive (+) and point X negative (-) or  ground.    The  resistor  should be connected at the panel end of the transmitter current loop close to the receiver input to take advantage of the immunity  of  the  current  loop  to  electrical  noise  pickup. Most electronic component distributors stock a 249 r, /2 watt, i±% tolerance metal film resistor which is adequate for this application. (page 3-710)