Multimeter use EX1 How to test Amps with a multimeter

Test    Amps    with    a    multimeter   

A  multimeter has current  test  range ,  uA   mA  A , the maximum current  that  the multimeter can test depends  on  multimeter  model  10A or  20A .  Analog multimeter can test DC current only but Digital multimeter can test  DC current and  AC current , some important information is printed on multimeter.  Be careful when  testing  DC current  because   it  has a  polarity  and current  flow direction , user must  properly connect the test leads  and  select   the  appropriate  range.

            Digital multimeter can test DC and  AC current  range  uA  mA  A

             Digital  multimeter  can  test  DC and  AC current  range  uA  mA  A

                Analog   multimeter  can  test  only  DC  current  ,    DCmA  range

Step  to  test  Current.

Simple circuit will be used  for  current  test  demonstration.

1. Estimate current amount and seek information  from label , manual  and  calculation.  For example from  simple circuit below  ,  from equation  V= IR  ,  I = V/R  so   9VDC / 1K ohm =  0.009A or   9mA   

2. Select   the  properly  range  for  target  measured  current. For sample  circuit below , the suitable range is  mA range ( for digital multimeter) and  250mA  range  for  analog  multimeter.  Turn  range switch  to  that   range.

3. Plug the red test lead  to + terminal  and   the black test lead    to - Com  terminal.

                                   Simple circuit  to demonstrate  current    testing.

4. Always  turn off   circuit before connecting with  the multimeter test lead.

5.  Connect   the  test  leads  with circuit  as   photo.   For current testing  , it   must connect multimeter series connection with   circuit.

6. Double check   if  the test  leads properly connect   and  set  the right current range has chosen. Be careful  DC current  has a  polarity and current flow direction  , wrong connection will cause multimeter damage.

7. After double checking   polarity  and   the right  range  , then  turn on   the  circuit.

       Multimeter series connection with simple circuit  to demonstrate  current testing.

8. Read the current on  display.  It  can change range to higher or lower range  if  scale is not  easy to read.  Before changing any range ,  always   disconnect   the test  lead and  turn off  the circuit  first.

  Plug the red  test lead  to A terminal  as  mA socket is not suitable for 9mA (over range).

                  Select   20m   DCA  for  testing  9mA target measured current.

Select   25DCmA   for  testing  9mA  target measured  current.  Reading  from  scale 250 Scale , Full scale 25mA will point at 250. This case it point at  90  so  the  reading  current  is  9mA

 

The   appropriate  DC  range  selection for  analog multimeter.

DC 50uA     for testing      0 - 50uA          ,  suitable   for  0-50uA

DC 2.5mA   for testing      0 - 2.5mA       ,   suitable   for  50uA-2.5mA

DC 25mA    for testing      0 - 25mA        ,   suitable   for  2.5mA-25mA

DC 250mA   for testing      0 - 250mA      ,   suitable  for  25mA-250mA

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30 testing of electronic devices

Multimeter use EX2 how to check voltage with multimeter

Check    voltage    with    multimeter   

Multimeter  can   test  voltage , current , resistance.   Check  voltage with digital  multimeter is easy to read the measured value  as  it  a  numberic  displays.  Check  voltage  with  analog  multimeter will explain too.

Step   to   check  voltage  with   multimeter.

The most important   point to  check  voltage  with   multimeter is the  appropriate range selection and the right test leads connection.

1.  Estimate the target voltage amount  , seek information from  device label , manual ,calculation. Unknow voltage  must  set  voltage range to the  highest range.  For example test  6VDC battery use 10VDC range (analog  multimeter )  ,  220VAC socket  use 250VAC range.  Low cost digital multimeter  must choose range by manual  but  advanced digital multimeter can  provide  auto range.

2. Plug the red test lead to  V terminal  and the black test lead to  COM terminal  , see photo.  While testing  do not touch the tip of test leads  ,  always hold at insulated area of  test leads.

3. Turn  range   switch   to the   appropriate range ,  DCV range  for testing  DC voltage and  ACV  range  for testing AC voltage.  Some model of  digital multimeter has auto range but some model of digital multimeter has not  ,  you have to select the suitable range by manual   , for example 6VDC battery  choose  20DCV range to check.

                     6VDC battery select  DCV range to check ,  the  multimeter  has  auto  range.

DC voltage has polarity so it  must connect  red test  lead to  positive terminal ( V+) and the black test lead to negative terminal ( V-).

6VDC battery select  20  DCV range to check , the multimeter has not  auto range so user must  select  the  appropriate  range  for   target  voltage.

    The target   voltage   across   resistor  is  DC  voltage  so  select  DC range  to  check.

 Select   10DCV  range  to check  6VDC battery and read value  from 10 DCV scale.

In this case  multimeter  point   at  5.9VDC.

4.  Disconnect the lead tests before changing the  voltage  range.

5. Read the measured value from display.

  Select AC voltage range to check  220VAC socket.  AC voltage has not polarity so it can switch test leads.

Select  250ACV  range to check  220VAC socket.  AC voltage has not polarity so it can switch test leads.   Read measured  value   from  250ACV scale , this case reading is about  210VAC.

The  appropriate  AC Voltage range selection

ACV 10      range     for testing  0-10V        , suitable for  0-10V

ACV 50      range     for testing  0-50V        , suitable for  10-50V

ACV 250    range     for testing  0-250V      , suitable for  50-250V

ACV 1000  range     for testing  0-1000V   , suitable for  250-1000V

The  appropriate  DC  Voltage  range  selection

DC 0.1      range     for testing  0-0.1V        , suitable for  0-0.1V

DC 0.5      range     for testing  0-0.5V        , suitable for  0.1-0.5V

DC 2.5      range     for testing  0-2.5V        , suitable for  0.5-2.5V

DC 10       range     for testing  0-10V         , suitable for  2.5-10V

DC 50       range     for testing  0-50V         , suitable for  10-50V  

DC 250     range     for testing  0-250V       , suitable for  50-250V  

DC 1000   range     for testing  0-1,000V    , suitable for  250-1,000V

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How to check electronic device

Multimeter test EX1 test diode with advance digital multimeter

Test   a    diode   with    advanced   digital   multimeter    

Advanced    digital   multimeter  has  many useful test function , it  is suitable for industrial use , technician level  and also fit  basic measurement.  It  provide  both auto  range  and manual range setting , high DC and AC current test function and  some  model  add  temperature measurement.  Another key feature it passed  higher safety standard CAT III  , CAT IV  level  which  will print on multimeter to indicate and ensure safety ,   level  of  usage.    Low cost digital multimeter can  set  range by manual only so it is suitable for  student ,  DIY circuit  ,  basic  repairing.  Here  it  will  use advance  digital  multimeter to test diode.   Is  it easy  to use  ?   ,  measurement  below  will   give  an   answer.

   Advance  digital   multimeter  for industrial and complex measurement , technical level

                               Low cost   digital  multimeter  for   basic measurement.

      CAT IV  Measurement  Category  level  is  suitable   for   industrial   measurement.

Step to test  diode  with  advance  digital  multimeter.

1. Insert the red test lead to  V Hz ll   terminal and   the  black test lead to  COM terminal.

2. Turn the range switch to  Diode  Test. The screen will display diode symbol  as  above photo No.1

3. Forward bias to diode , connect the red test lead to Anode terminal and black test lead to  Kathode terminal.   Good diode will display 0.3-0.8V.  Shorted  diode  display  000 , open diode display OL.

                                Kathode  terminal  has  white stripe indication.

  Forward bias to diode  ,  good diode will display  0.3-0.8V  forward  voltage  drop

4. Reverse bias to diode , connect the red test lead to Kathode terminal  and the black test lead to Anode terminal.  Good  diode  will display   OL.   Shorted  diode  display 000 ( or very small amount such as 002)

                               Reverse bias to diode    ,  good diode will display  OL.

4.  Shorted  Diode will display  000 ( or very small amount such as 002)  for forward biasing and  reverse biasing.  Switch the test   leads also  still  get  the same display as 000.

          Shorted  diode will display  000 ( or very small amount such as 002)

4.  Open   Diode will display  OL    for  forward biasing and  reverse biasing.  Switch the test  leads also  get the same display as  OL.

    Open  diode will display  OL   , switch the test   leads  still   get  the same  OL  display.

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How to check electronic device

Multimeter test EX2 test a diode with Digital multimeter DT-830B cheap multimeter

 Test    a   diode   with   Digital   multimeter    DT-830B 

The   digital   multimeter model  DT-830B  has  a diode check range ,  It  is  a  cheap  multimeter so some testing display may different from  an  advance and higher price multimeter.   Its  diode check range will supply  2.8V and 1mA test current so you can use it to check  LED  and  Zener diode  too , as it supply very small test current to save battery life time so  LED does not light , however , it still indicate good or bad condition  by  display  voltage  drop.

Step  to   test  a   diode  with   cheap  multimeter.

1. Insert the red test lead to  VΩmA  terminal  and  the black test lead to COM terminal.

2. Turn the range switch to  Diode check and it  will  display    number 1    as above photo.

3.  Forward bias to diode by connecting  lead test with diode as below. Note the testing is done when diode is not on circuit and  there is  no voltage present on diode.  Always remove power source from diode before testing.

 Forward bias to diode ,  good diode will display some forward   voltage drop and the unit is mV  so this testing value  is  536mV   ( 0.536V) 

4.  Reverse bias to diode connect test lead with diode as photo below.  The good diode will display number   " 1 ". ,  it   mean  ∞  Ohm  (  not connected  or  not  shorted  )

   Reverse bias to diode , good diode will display number  "1"  mean  ∞  Ohm  (  not connected  or  not shorted  )

5. Bad diode  (shorted ) always  display  000  for  forward  biasing and reverse  biasing.

   Shorted  diode  always  display  000 , switch the test lead  it still get the same display 000

6. Bad diode  ( open ) always  display  number "1"   for  forward  biasing and reverse  biasing. This Time is mean  ∞  Ohm  as  diode open so there is not forward voltage drop display and no current flow when   forwarding biasing.

    Open  diode  always  display  "1" , switch the test lead it still get the same display "1"

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How to check electronic device

Multimeter test EX3 test mosfet with digital and analog multimeter

Test  mosfet   with   digital   and   analog   multimeter  

A  power  component  has  high current , high wattage  may be broken  as  shorted condition and  open condition.    Before  other  process testing , you may  firstly   check  shorted condition and  open condition. Testing  mosfet   has some detail and  all steps of testing  must be good so it is a good mosfet. If  any of  only testing step is fail   , the mosfet  is already  broken.

                                        N   Channel   MOSFET  Symbol

                                          P   Channel   MOSFET Symbol 

Step  to  test  mosfet  with  a  digital   multimeter

1.   Discharge mosfet .  short  3  terminals  D-G-S  together by using resistor legs or  other   metal wire. then remove resistor  leg.   After  shorting  3 terminals , do not touch any mosfet terminal again.  If  you touch it by error , it must re-discharge.  The area which  can touch and hold  is the black case of mosfet.

2.  Test  G and D  terminal , read the measured value.    Switch the test lead and read the measured value again.   A  good  mosfet ,   meter   will   display  "OL"   2   time.

   Discharge mosfet .  short  3  terminals D-G-S  together  , G   D  S  is terminal arrangment.

                                Test  G and D  terminal.  The  first testing.

                    Test  G and D  terminal.  The  second  testing ( switch the  test lead)

3.  Test  G and  S terminal , read the measured value.    Switch the test lead and read the measured value again.   A  good  mosfet ,   meter  will   display  " OL"   2  time.

                                 Test  G and S  terminal.  The  first testing.

                                  Test  G and D  terminal.  The  second  testing ( switch test lead)

4.  Test  D and  S terminal.   Use Ohm range to test D and S terminal  and read the measured value.  then switch the test lead  and  test again.  A good mosfet will display  " OL "   1 time  and  display high resistance  1  time. Some model   of  mosfet  has internal diode connect across D  and  S terminal , this case you can use diode range to test it.     Bad   mosfet will display differnt ways that is  , shored will display very  low resistance  0 Ohm  2 time  , open mosfet will display " OL"   2 time. 

      Test  D and  S terminal.   Use Ohm range will display high resistance  1 time.

        Test  D and  S terminal.   Use Ohm range will display  " OL "  1 time.

Please be careful after discharge mosfet ,don't touch any terminal. Always hold mosfet at  insultated case.

Step  to  test  mosfet  with  a  digital   multimeter

1.   Discharge mosfet .  short  3  terminals  D-G-S  together  by using resistor legs or other   metal wire. then remove resistor leg.    After   short   3 terminals , do not touch any mosfet terminal again.  If  you touch it by error , it must   re-discharge.  The area which  can touch and hold is black case of mosfet.

2. Test  G and  D  terminal.  Set  range   to Rx10K and do zero ohm adjustment.   Connect test lead with D and G terminal    then read the measured value. Switch the test  lead and read the measured value  again.

Good   mosfet  , the  pointer  will  point  at   ∞     2   time.

3.  Test  G and  S  terminal.  Set range to Rx10K and  do  zero ohm adjustment.  Connect test lead with G and S terminal   then   read  the  measured value. Switch the test  lead and read the measured value  again.

Good   mosfet  ,the pointer  will point at   ∞    2   time.

    Test  G and  D  terminal.  Good   mosfet  ,  the pointer  will  point   at   ∞     2   time.

   Test  G and  S  terminal.  Good   mosfet  ,  the pointer  will point at   ∞     2   time.

    4.  Test  D  and  S  terminal.  Set  range  to Rx10 ( or Rx100  )   and  do  zero ohm adjustment. connect test lead with D and S terminal   then read the measured value. Switch the test  lead and read the measured value  again.

Good   mosfet  ,the pointer  will point at   low   resistance   1    time.

Good   mosfet  ,the pointer  will point at    ∞  (or  high resistance )  1    time.

( some model  it will  point   at  high   resistance instead of  ∞  )

          Good   mosfet  ,the pointer  will  point at   low resistance   1    time.

      Good   mosfet  ,the pointer  will point at    ∞  (or  high resistance )  1    time.

Bad mosfet when  test  D  and  S  terminal  , shored condition will display  0 ohm  2 time.

Open condition  will display  ∞   2  time.

Shored    mosfet   will display  0 ohm 2 time when test D and S terminal

                         Open mosfet   will display  ∞   2  time  when test D and S terminal

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How to check electronic device

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  range   at  BUZZ  range.

                                                  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.

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

  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.

 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.

 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.

     Switch ON position ,  contact is connected and multimeter display low resistance = good switch

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

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How to check electronic device