Section  3  —  Sensors 
38 
Set up Tachometer 
 
A  tachometer  collects  information  about  a  machine's  rotation  speed.  It 
provides  you  with  an  exact  reading  of  machine  speed  as  a 
measurement  is  taken.  This  is  more  accurate  than  using  a default  RPM 
because  a  machine's  speed  can  vary  significantly  under  different  loads. 
 
The  tachometer  also  provides  information  on  the  angle  at which  the 
rotor  is  vibrating.  The  angle  is  measured  from  a  fixed  reference  mark  on 
the  rotor  called  the  phase  angle.  To  balance  a  rotor,  you  need  to 
consider  the  amplitude  of  vibration  and  the  phase  angle.  The  amplitude 
shows  the  severity  of  the  imbalance.  The  phase  angle  indicates  the 
geometry  of  the  imbalance. 
 
WARNING! The laser tachometer is a class 2 laser product. Do 
NOT stare into the laser beam. 
 
To  set  up  your  tachometer: 
1.  Screw  the  block  grip  extension  of  the  tachometer  into  the end  of  the 
mounting  base  articulated  arm. 
2.  Plug  the  cable  socket  into  the  tachometer  connecting  pins  >  Turn 
the  locking  ring  to  make  the  connection  secure. 
3.  Locate  the  TACH  input  on  your  instrument  >  Attach  the  other  end  of 
the  cable  to  this  (the  LEMO  end). 
4.  Stop  the  rotor. 
5.  Cut  out  a  small  strip  of  the  reflective  tape  supplied  (approximately  5 
mm  x  15  mm  (0.2"  x  0.5"). 
6.  Stick  this  piece  of  reflective  tape  to  a  machine  part  that  rotates  at 
the  rotor  speed  (e.g.  the  shaft).   
 
NOTE: This trigger spot should provide a pronounced increase in 
reflection as it passes under the tachometer light beam. The tape 
width must be at least double the diameter of the light beam spot. 
 
7.  Mount  the  tachometer  magnetic  base  to  a  stationary  portion  of  the 
machine,  close  to  the  trigger  spot. 
8.  Position  the  tachometer  slightly  away  from  the  center  line of  the 
rotating  machine  part  so  that  reflections  from  the  surface  of  the 
machine  part  do  NOT  interfere  with  it.   
 
 
9.  Start  the  rotor  >  Wait  until  it  is  running  at  normal  running speed. 
10.  Open  the  main  menu  on  your  instrument.   
11.  Press    to  access  the  Measure  menu.