Multimeter use how to test DIODE by multimeter

HOW     TO    TEST    DIODE    by   digital   multimeter   and  Analog multimeter    Test  Diode


Diode   is  a  basic electronic device and it  has wide application  on   many  circuit such as  rectifying , switching ,  protection circuit  , polarity protection  etc. Before checking   it  need to know  a necessary information about diode.   Diode has many package below is some example. On its body  has  shown  diode symbol so that you  can  know its   terminal function   anode or cathode.

This   is  a   symbol  of  diode ,  Anode for  positive voltage ( + ) and  Cathode for negative voltage.   If   supplying  the right polarity voltage  to  the   diode  terminal  ... V+   to  anode and V-  to cathode   this  called  " Forward  Bias "    this case diode will let current flow.  If   supplying  reverse polarity to the  diode ..... V-  to  Anode terminal  and  +  to  Cathode terminal ,  this case diode will block current and  no current flow   this called reverse bias.   In case of  reverse bias there is only  leakage current  flow and  amount  as uA or  mA  for  Germanium Diode and  there is   not  any leakage current  for  Silicon Diode.

Test  Diode
Example  of   Diode  Package 

Diode symbol

DO package  (  DO = Diode outline )

Stud  package  it   has screw and nut to tighten the wiring  connection.

Diode  2 pin
TO-220-2   package  has  2 terminal  and  TO-220-3 package has  3 terminal.

Module  package   it  use  for  high current and high voltage diode. Inside the module  may consist of  1 or  2  or 3 or  4  diode ,  it   depends  on diode part number.  On  module ,  there is  diode symbol and internal wiring  connection  for   technician  to install  and   test   it.

Diode  Module 

Step   to   check   Diode .
This  testing   is  a  off-board  testing.

1.  Turn  rotary switch of  multimeter  to Diode test  Function  as   photo.  On  display will show diode symbol and multimeter  knob  will  direct  to  Diode symbol  too.

testing electronic components with multimeter
Diode   test   Function

2.  Connect  red  test lead to  anode  and  black test lead to cathode terminal  ( forward bias )  . Note that the white  band  is  Cathode terminal . you will see  voltage drop across diode 0.5-0.8V  for  Silicon Diode  and   0.1V - 0.3V  for  Germanium diode.  Switching  the test leads ;  red to Cathode pin and black to Anode pin ,  the good diode will  display as     " OL " ( Over Limit )

Diode  terminals  :  Cathode and Anode.   Test  DIODE
Good  diode  has  voltage drop across diode =   0.5-0.8V  for  Silicon Diode  ( forward bias).

DIODE  test  with  Multimeter
    The good diode will show  " OL "  when supplying  reverse  bias.

 Good diode  there is  voltage drop across diode =  0.1V - 0.3V  for  Germanium diode (forward bias)
test    multimeter   Test   DIODE
Voltage drop across  Germanium diode  diode =  0.1V - 0.3V.


Check  DIODE
The good  diode will  display  as    " OL "  when  supplying   reverse bias.

If   it is   a  bad  diode  ( open ) ,   it  will  show  " OL "  2   time for  both  the  first measurement ( forward bias) and   the second   measurement    ( reverse bias )  as photo below.

Check  test
Bad  diode  ( open ) ,   it  will  show  " OL "  2   time.

If   it  is  a    bad   diode ( shorted ) ,   it  will  show  "  very low  voltage drop "  2   time for   both  the first measurement ( forward bias)  and   the second measurement  ( reverse bias )  as   photo below.    DIODE  test
Bad   diode ( shorted ) ,   it  will  show  "  very low  voltage drop "  2   time.

Test     IGBT    Part    2

Step   to    check    Diode   by   Analog  Multimeter.
Before checking  it  need to know the real polarity of  voltage  from the  test leads. The color of  test lead  may  cause   confusion to  begin learner.  Red is for  positive (+) that correct ,  but , when we  set  the knob  of  analog  multimeter to resistance  test  function  the red test lead connect to negative polarity of internal  battery so the red test lead supply V-.    The  black test lead connect to the  positive  polarity of internal  battery so the black test lead supply V+.  Summary  red test lead  = V -  and  black test lead = V+  .   See diagram below to simplify.
Test   leads   connection  diagram of analog  multimeter.

1.  Turn rotary switch of   analog  multimeter to  Rx1 range resistor test  function  for medium and big diode testing  ,  Rx10 range  for small diode   testing.
2.  Forward   bias  checking ,  connect   the  red test lead to  kathode terminal  (  note  kathode terminal   has white band )  and  the black test lead to  anode terminal .   The good diode  will display low resistance   and   LED  on  the multimeter  light     as  shown photo below

Test   diode
Forward   bias  checking , good diode ,  present low resistance.

3.  Reverse   bias checking  .. connect the  red test lead to Anode terminal   and  black test lead to kathode terminal .  The  good  diode  will display very very  high  resistance the pointer point at   ∞   infinity  as shown on   photo below.   HOW   TO  TEST   DIODE
Reverse  bias checking , good diode , the pointer  point at  ∞   resistance on  scale.

4.  If   it is  a  bad diode ( open ) ,  it  has very high  resistance the pointer point  at   ∞ scale  (infinity)  2   time ....for  the  first measurement ( forward bias checking ) and the second measurement  ( reverse bias checking )  

5.  If  it is a bad diode (shorted )  ,  it  will  show "  very low  resistance nearly  0 ohm   2   time for the  first  measurement ( forward bias checking  ) and  the second measurement  ( reverse Bias checking )  shown  as   photo below.

Test  Diode
Bad  diode (shorted )  ,  the pointer point  at    0 ohm   2   time.