Section  7  —  Analyzing  Measurements  Onsite 
130 
Tips for Taking Measurements 
 
Here  are  some  tips  to  consider  when  taking  measurements: 
•  Use  the  operating  mode  typical  of  the  machine  in  question  (e.g. 
typical  load  and  running  speed).  This  will  ensure  the  loads  on 
the  components  (e.g.  bearings)  are  the  same  as  those  that 
define  their  wear.  For  multi-operating  mode  machines,  it  is best 
to  take  measurements  when  the  loads  on  the  bearings  are  at  a 
maximum.  Ensure  you  take  all  future  measurements  in  the 
same  mode. 
•  Ensure  you  do  NOT  lean  on  the  machine  or  place  a  heavy  object 
on  it  (e.g.  a  heavy  tool  box).  Doing  so  will  change  the  vibratory 
behavior  of  the  machine. 
•  Stop  any  machines  that  are  operating  near  the  machine  you  are 
measuring  (if  possible).  Machines  operating  nearby  can  affect 
the  vibration  of  the  machine  you  are  measuring. 
•  In  addition  to  taking  measurements:   
•  Stop  and  listen  to  the  sound  of  the  machine. 
•  Look  for  loose  bolts  and  oil  leaks. 
•  Check  whether  any  machine  parts  that  are  vibrating  visibly. 
•  Touch  the  machine  to  check  for  hot  bearings. 
•  Touch  the  area  that  is  vibrating  (e.g.  with  a  screwdriver)  to look 
for  symptoms  that  might  later  aid  vibration  analysis  (if  it  is safe 
to  do  so).  
•  If  you  have  a  stroboscope,  you  can  use  this  to  freeze  rotating 
shafts,  belts,  and  couplings.  This  will  enable  you  to  observe  the 
operating  shapes  and  relative  speeds  of  these  parts,  which  will 
help  with  later  vibration  analysis. 
 
MORE: See Strobe Output for more information on using your 
instrument to automatically control strobe frequencies.