Sunday, January 31, 2021

Continuity check and test continuity with a multimeter

Test   continuity  with   a   multimeter

Continuity checking  is  used  to  testing   the connection :  shorted  condition  of  wire , switch contacts , relay contacts ,  PCB  trace.   Both  analog and digital multimeter has continuity test function.  Some model of digital multimeter  has not continuity check , in this case , you can use Ohm range to check  continuous of components.  Note that  continuity check  is  a  testing when there is  not  voltage present  on component  so  make  sure if  the component   is  unplug , switch off .


Step to Continuity check.

1. Rotate range switch to BUZZ ( X1) range.

2.  Check  multimer is ready to use  by  0 ohm adjustment ; shorted  2  test leads  then  the buzzer will sound and at the same time  LED light up  this means  multimeter  is  ready   to  test.


Continuity check  and  test  continuity with  a  multimeter
                                 Continuity check  range   at  BUZZ  range.


test  continuity   with  a  multimeter
                                                  0  ohm adjustment

3.  Make sure that  if  there is  not any voltage present  at  component under test  , unplug  or switch off should do before testing.   The  multimeter  will  damage  if  there  is  voltage  while  doing  continuity check.

4. Touch the test leads  with component under test.   For example AC power cord ,   the buzzer will  sound   and  LED  light  up  if  it   is  a   good AC power  cord.


test  continuity
          The buzzer will  sound  and   LED  will  light  up   for   good AC power cord


Test  with  Multimeter
  The buzzer will  not  sound  and  LED  does not light  up  for  open  AC  power  cord


5.  In  case  of  checking  relay contacts , switch contact.     It depend on contacts type.

NC Contact type ( normally close) , the buzzer must sound , mean good contacts. If there is not any sound heard , mean bad contacts.   NO Contact type  ( normally open ) , the buzzer must not sound , mean good contact.  If  there  is  sound heard , mean bad contact.


test  continuity
 NC Contact type ( normally close) , the buzzer must sound , mean good contacts.  If  you press the roller lever causes  switch contact change position , the buzzer will not sound.


Test  with  Multimeter
 NO Contact type  ( normally open ) , the buzzer must not sound , mean good contact.   If  you press the roller lever causes  switch contacts  change position , the buzzer will   sound.



Some model of multimeter  there  is  not a  continuity check function. It can use Ohm range to check continuity.  It  will display low resistance for  continuous condition and display OL or  1 for open condition.

test  continuity with  a  multimeter
     Switch ON position ,  contact is connected and multimeter display low resistance = good switch


test  continuity
     Switch OFF position ,  contact is disconnected and multimeter display  1 or  OL = good switch