Monday, April 13, 2020

How to check a capacitor with a Multimer Analog and Digital Multimer Measurement

How   to  check  a   capacitor  with  a   Multimer

Capacitor  is  a  basic components  that  use  a  lot  on  PCB.    Film capacitor and ceramic capacitor has not polarity  ,  but tantalum capacitor and electrolytic capacitor  has  polarity.  Always discharge big capacitor and high voltage capacitor before testing  and   test  it   when  there is  not  voltage  present  at the  circuit.  Unplug  and  remove power from circuit before measuring.  Failure to provide those condition before testing it  is  a  high risk of electric  shock and the  multimeter will damage too.

Step   to   check    a   capacitor  with    Digital    Multimer.

1. Must  remove power ,  switch  off   and discharge big capacitor , high voltage  capacitor  before testing.   Test capacitor  is performed   when it  is  not  on  PCB ( not connected  on circuit).

2. Turn the switch range to capacitor test function.

3. Connect  the  multimeter  test leads with capacitor terminals. 

4. Read the measured value.  

Good capacitor will get  measured value closet to  it's  value  that  print on label.

Shorted  capacitor  will  display  OL.

Open capacitor will display  nF  value  which is capacitance  of  test leads  only.

Degrade capacitor  , measured  value  is  too low and  amount is  different from original value.

Capacitor check
   100uF capacitor , get measured  value as  98.9uF which is close  to printed value ( good capacitor)

How   to  check  a  capacitor
  Multimeter display for  internal  open  capacitor ( For demonstration purpose only )

Test Capaictor with Multimeter
  Multimeter display  for  internal  shorted  capacitor   ( For demonstration purpose only )

Capacitor  Test
   Film capacitor 5uF ,  get measured value as  5.16uF  which is close to printed value.

Step to check a  capacitor  with    Analog    Multimer.

1.  Must remove power ,  switch  off  and discharge big capacitor , high voltage capacitor before testing. Test capacitor is  performed  when it is not on PCB ( not connect on circuit).

2.  Turn rotary range switch to appropriate range  as  list  below.

X10K    for  capacitor  value :  less then 10uF

X1K     for  capacitor value : 10uF  -  47uF

X100    for  capacitor value : 47uF - 470uF

X10       for  capacitor value : 470uF  -  4700uF

X1         for  capacitor value : 4700uF and  more value

The good  capacitor , the needle will  move  forward  then  backward at the end of scale. Electrolytic capacitor has very  little  leaked current  so  the needle will not fully move backward for some capacitor.

                  The  needle  will  move  forward  then  backward  at  ∞  for a  good capacitor.

check  a  capacitor
                 Leaked  capacitor  is  a bad capacitor , the needle  does not move  fully  backward  at  ∞ but it  point  at  some  high resistance. Switch the test leads and re-test , it will get the same testing result.

How to check  a  capacitor
Open  capacitor  is a bad capacitor , the needle will not  present  any movement ,  it  always  point  at ∞   scale .  Switch  the test leads and re-test , it will get the same testing result.

How  to  check  a  capacitor

Shorted  capacitor  is a bad capacitor , the needle  move forward  and  always  point  at  0 ohm   scale . Switch  the test leads and re-test , it  will get  the  same  testing  result. ( this photo for demonstration only )