Multimeter use how to test MOSFET

How   to   test    MOSFET  with   multimeter

Multimeter   use   how   to   test    MOSFET  with  Digital  Multimeter   and   Analog    Multimeter 

MOSFET  TESTING    Mosfet working principle  is  input voltage control output current  , we can use  basic bias to test whether it is a  bad or good mosfet .  Mosfet has  Gate  Drain and source legs , take  part number  to find  leg function from datasheet then connect test leads as photo. Note  analog  multimeter on this testing  when set to  resistor  test function or Ohmmeter  , the black test  lead supply  V+  and  the red test lead supply V-  ; the reason is  the black test  lead is connected with positive polarity of internal battery and the red test lead is  connected with negative  polarity of internal battery. If you are unsure about polarity of  your multimeter test leads , you can check it with  multimer manual  or   ask   the multimeter  expert.

TEST   MOSFET  with Multimeter
TEST   MOSFET  with  multimetro  मल्टीमीटर
Connection diagram   to  test  MOSFET  with  Analog Multimeter.

Step to  check MOSFET  with  Analog Multimeter.

1.  Set analog multimeter to  Rx10K  as  this range the multimeter  will  supply 9VDC  from internal battery.  9VDC is  high enough  to bias gate leg so mosfet is working as  ON state.
2. Discharge  mosfet   by shorting  or connecting  3 leg  together  by  using  resistor's leg.   then do not  touch   the  legs.
3.  Connect test leads with mosfet leg as photo above
4. Use  resistor's  leg to temporarily  connect  between  G  leg and  D  leg ; the  pointer  of multimeter move  to  indicate  some  resistance  on ohm's   scale   as  photo.
5. After removing resistor's   leg  from mosfet's leg  the  pointer can  hold the same  position.
as  mosfet is  still working   ON state , good mosfet  will  work  like this.  but  the bad mosfet can not , the pointer  of multimeter  can  not  hold  the same position ( it  move  back  to  ∞ position ) after removing resistor's leg.
6. Test  OFF state ,  use resistor's  leg to temporarily  connect  between  G  leg and  S  leg.
the  pointer of multimeter  that  hold  the ON  stage  will not  be  ON  sate anymore because  - Voltage  from S  leg  will bias mosfet   to off  state.
7. Summary , good mosfet can bias to ON and OFF state  but    bad mosfet can not  bias  ON and OFF state.

Bias   Mosfet  to  ON state , temporarily  connect   G  and  D  leg

Good mosfet  hold the ON state  after removing  resistor's   leg , the pointer  stay the same position
but  bad  mosfet can not.

Bias   Mosfet  to OFF  , temporarily  connect   G and S  leg
The pointer that present the on state  will  move back   to 
∞  position ( OFF  state).

Step to  check MOSFET  with  Digital Multimeter.
1. Take   mosfet  part number  to find  leg  function from it's  datasheet.
2. Discharge  mosfet   by shorting  or connecting  3 leg  together  then do not  touch   the  legs.
3. If   there is  a  diode at D and  S  mosfet   leg  ,   turn rotary switch  of  Digital Multimeter to diode test function ,  some mosfet  has internal diode connected between D and S leg.
Good mosfet  has good diode  it  will display   0.5-0.8V across it  when  forward   bias testing    and display  " OL "  when  reverse  bias testing.
Bad mosfet   ( shorted )  will  show  000V.
Bad moset  ( open )   will show  OL  2  times.
4. If there is not  any  diode at  D and  S  legs of mosfet
Turn  rotary switch  of   digital  multimeter to  resistor   test  function.
testing  has  2 results .
Good mosfet will show  low  resistance   1 time  and   show  "OL"   1 time  (  E MOSFET )
Good mosfet will show  low  resistance   1 time  and   very high  resistance 1 time  ( D MOSFET)
Bad  mosfet will   show  results  as
Bad  mosfet (short)  show  0  ohm  2 time.
Bad  mosfet (Open)  show  OL   2 time.

 Some part number of   mosfet  has  diode connected between  D and  S  leg.

Example  MOSFET   has  diode at  D and S  leg  so  the  testing is as  same as Diode testing.

Example  MOSFET  has  diode at  D and S leg  so  the testing is as   same  as  diode testing.

5. Check  G  and D leg  , set  digital multimeter to  resistance test function.
 then  switch  lead tests  to do  testing   again.
Good  mosfet will show   OL  2  time  because there is insulator  at  gate junction  so  it  is very very high resistance  that   multimeter can not  measure .  Bad mosfet will show some resistance.
6. Check  G and  S leg  , set digital multimeter to resistance test function.
conduct testing  ;  then  switch leads  and   test  again.
Good  mosfet will show   OL  2 time  because there is insulator  at gate junction   so it  is very very high resistance that multimeter can not  measure .  Bad mosfet will show some resistance.