Multimeter use EX3 OL display on multimeter meaning and measuring Example

OL  display   on  multimeter meaning  and   measuring 

What  does  OL  mean  on  a multimeter ,  this  is  the  frequency ask question  from digital  multimeter  user.   It  has many meaning ,  it  depends   on  what is  the test  function range  that you set.   I  have researched from many   multimeter manual and  found  that   OL = Over a  range  Limit  and  other detail at  measuring  explaination   when  LCD  display " OL"  mean  Over  Range  and  it  suggest user to change the range to higher range or  seek the appropriate range for  the measured amount.  For  example when  you measure  9VDC battery  and use 0.000V range  by manual selection , the testing result display OL as photo , it mean this range selected  is  not suitable for 9VDC and you have to change setting to higher range.  OL  display also displays with  other  test function  range such  as  resistor  measurement , current measurement  , capacitor test  , temperature measurement  etc.    View photo below  for   more understanding.

OL display  ,  measuring   example  for  range selection is not suitable.

        0.000   DC voltage range  set  by manual  range selection  for  9VDC battery

  It  display OL  because  this 0.000  DC voltage  range  is  not suitable for  9VDC.

The solution  is  setting to auto range  or  use higher range.  (For   OL display example only)

                      00.00V  range set  by manual  range selection  for  9VDC  battery

  It  displays  9.43V as  it  should be  (mean  00.00  DC voltage  range  is  suitable  for  9VDC )

The good measurement , you have to select the right range and right  test function before operating any measuring. Unknown value  it suggest to chose the highest range first.   For advance multimeter it has auto range , but , for low cost multimeter has only manual range selection and user need to study how to set    the  suitable  range  for  the target measurement.

OL display  when testing  condition of  components  =  not shorted ,  not connected.

The other meaning of  OL  display  on  test  function such as  diode test , continuity check . It  indicates the  condition  of component  "good"  or " bad" , defective.   OL  display  for  diode check , In case of  reverse bias it  means   diode is  not  shorted ,  2 terminal is not connected and when supply reverse bias to diode it  has to display  "OL"  as  it  should  be  =  good diode.   Example will be shown  by photo. 

                 Forward  bias  to  a   diode  ,  it  displays  0.3-08V  =  good diode.

   Reverse  bias to a  diode  ,  it displays   OL =  good diode  and  this  time  OL  mean  "not shorted "

OL  display when we  use  continuity check.   When checking switch  at  OFF position it  has to be not connected , not shorted condition. This time OL display  mean contact is  not shored (good contact).  Technical  term  NO  terminal ( Normally  open) it mean contact is not connected and the testing result get  " not connected " as it should be.  When changing   the  switch position to "ON"  it  means internal contact  is connected  or  shored , the display should be  0 ohm for good contact.  If  the display still show OL  it  means  internal contact is not connected as it should be condition ,  so OL = bad contact.

           OFF position , internal contact of  switch  is not connected , OL display means contact is not connected.  So  switch  contact  is  good  as   it  should  be.

ON position , internal contact is connected ,  the display has to show 0 ohm ( shorted) for a good switch     If   display  show  OL  it  means   not  connected  contact  , this case  it is  a  bad contact ( switch)

 ON  position  ,  the  internal contact  is  connected , but , multimeter  display   OL  means  internal contact is not connected  as  it  should   be  so this case   it  is  a   bad  switch  contact.

Read    more   topics     of     testing   ,  from     here.

How to check electronic device

Multimeter use EX4 test AA battery and 9V battery with multimeter

Multimeter   use     test    battery 

Analog  multimeter  has 1.5V  BATT range  and  9V BATT range  for especially  testing  small battery. BATT range operation  is   different   from  DC voltage range.    BATT  range  has  accurate measurement  and  precise  method to test AA and 9V  battery.  BATT  range  has  internal  low  value   resistor  and when set to this range  the  current  from test  battery will  flow through  the resistor and there is some voltage across the resistor , the multimeter will display voltage from  the resistor.   But , DC voltage range is tested while test battery is open circuit (current does not flow) because DC voltage range has high  input impedance so it is not  a  precise measurement to test AA and 9V battery  , however ,  In many case  it  is  still  useful to test battery with  DC voltage range (Rough or approximate  measurement).

Step  to  check  1.5V  9V  battery  with   multimeter.   

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

2. Turn  range switch  to 1.5V BATT for testing  1.5V  AA  battery  and   9V BATT  for  testing  9V battery.

                                  Test  AA  1.5V   battery  with  1.5V  BATT  range

                                Test   9VDC    battery  with  9V  BATT  range

                                            Battery  test   range  ( BATT)

3.    Reading the test result.

Good  battery :  the pointer will point  at  Good scale area.

Good  or  bad ?  :  the pointer will pint at  Scale ? area , this condition battery can be used for low current consumption device , such  as wall clock  , but not suitable for  device  need  power.  

Bad :  the pointer will point at  Bad scale area , it's time to change  a  battery.

Some analog  multimeter and digital multimeter has not  BATT range , this case it  will  use DC voltage range to check battery  but is not a precise measurement to test battery.   DC voltage range to test battery is   approximate  measurement  which  is still useful  and  acceptable  for many case.

Read    more    of    testing.

How to check electronic device

Test NPN PNP transistor with a digital multimeter and identify transistor pinout

Test  NPN  PNP   transistor   with  a   digital    multimeter 

Test condition of  electronic   component   start  with  test   resistor , capacitor , diode , LED , and the next component is  transistor.   Before testing  transistor  you have to study how to test diode firstly  because it the same process just  more detail.   The parity of  test  leads  and  diode , forward bias , reverse  bias  also use to describe how to test transistor.   Diode model is used to explain how to test transistor.   NPN type 2 diode is common anode connection   and  PNP type 2 diode is common kathode connection.

NPN   Transistor and   2    diode model  to test  NPN  type.

                                     PNP   Transistor and   2    diode model  to test  PNP   type.

Step to  test    transistor   with  a   digital    multimeter .

1. Turn the range switch to  diode test.

2. Connect the test  lead with B and C terminal and read the measured value.  Then switch the test leads and  read the measured value again .  Good transistor will  display  0.5-0.7V    1  time  and  "OL"  1 time. Shorted transistor  will  display 000V  2 time  and  open transistor  will  display "OL"   2 time.

 The  terminal   arrangement   of   example  transistor for  test demonstration.  Different transistor part   number may   has  different terminal  designation.

       B  and C terminal  test , good transistor will  display  0.5-0.7V    1  time.

   B and C terminal  test , good transistor will  display  "OL"   1 time. ( switch the test leads )

3. Connect the test  lead with B and E  terminal and read the measured value.  Then switch the test leads and  read the measured value again.   Good transistor will  display  0.5-0.7V    1  time  and  OL   1 time. Shorted transistor will display 000V  2 time  and  open  transistor  will  display  OL   2 time.

           B  and  E   terminal  test , good transistor will  display  0.5-0.7V    1  time.

  B  and E  terminal  test , good transistor will  display   OL   1 time. ( switch the test leads )

4. C and E  terminal test , connect the test  lead with C and E  terminal and read the measured value.  Then switch the test leads and  read the measured value again.   Good transistor will  display  OL   2  time and  shorted transistor will display 000V  2 time.  

5. All  step of  testing  must  be  all  good condition  so the transistor is  still  good  ( step 2 , 3 and 4 :  B-C terminal test , B-E terminal ,C-E terminal test).   If   there is only any of  1 step  fail   , that transistor   is  bad.

                 C and E  terminal test  ,   good transistor will  display  OL   2  time

   C and E  terminal test  ,   good transistor will  display  OL   2  time ( switch the test lead )

Identify  transistor pinout.

1.  Find  B  terminal ,   from   2   diode model  at  the beginning  ,   random the test around   6 times and you will find 2 time that the meter display  0.4-0.7V , the  B terminal is  connect with any test lead (not move) and make  the other test lead that  move to terminal no.2 and no.3 and meter  display  0.4-0.7V  2 time ( B-C , B-E). From  2 photo below so the red test lead is  B  terminal.

2.  Find  C and E  terminal ,  V BE  >   V BC  ,  V BE  is more than V BC so  terminal  No.3 is  E terminal  and   terminal  No.2 is  C  terminal.

                                 Hold   the  red test lead with terminal no.  1

 

Hold   the  red test lead with terminal no.  1

--------------------------------------------------------------

Choose   these   articles    to   read   more    ,   from   here  .

Test    IGBT   Part   1

https://www.testmultimeter.com/2021/11/multimeter-use-how-to-test-igbt.html

Test    IGBT   Part   2

https://www.testmultimeter.com/2020/12/test-igbt-with-multimeter-bad-or-good.html

Test    SCR   Module  

https://www.testmultimeter.com/2020/12/test-scr-thyristor-module-with.html

Test   IGBT    Module 

https://www.testmultimeter.com/2020/12/how-to-to-test-igbt-module-with.html

• 1)   30 testing of electronic devices
• 
  

2)   Test  Triac   with   multimeter

3)   Test   SCR   with   multimeter

4)   Test   MOSFET   with   multimeter

------------------------------------------------------------

Test a Diode with Analog Multimeter check foward voltage drop forward current and reverse current.

Test  a   Diode   with   Analog    Multimeter

We  use LV and LI scale to test a   diode condition.   How to set  those scale ,  it use Ohm range then reading the  measured value  from  LV scale to test  forward voltage drop (Vf)  and   use  LI  scale to test  forward current  and reverse current.  This  method can  test  LED and  zener  diode  too.  See photo below ,  LV scale range   0 - 3  full scale  and  LI  scale  range  0-15  full scale.

LI scale reading  0-15  full scale.

x1     Full Scale  150mA    ,  multiplied by  10   with 0-15 reading 

x10   Full Scale  15mA      ,  multiplied by  1     with 0-15 reading 

x100  Full Scale  1.5mA    ,  devided by  10       with 0-15 reading 

x1K   Full Scale  150uA    ,  multiplied by  10    with 0-15 reading 

                                 LV scale range   0 - 3    and   LI  scale  range  0-15

Step  to  test   Diode   with  analog    multimeter .

1.   Set the multimeter to Ohm range.  Select the right range and turn rotary switch to  suitable  range. Multimeter will supply voltage and current to diode from the  test leads.  The voltage and current supply from internal AA  battery which installed inside the multimeter.

Rx1 ( 150mA 3VDC )      for  big  diode. 

Rx10 (15mA  3VDC )      for medium diode.

Rx100 (1.5mA  3VDC )   for small diode

Rx1K ( 150uA 3VDC)     for test leaked current.

2.   Plug the red test lead to +  terminal and  black test lead to COM terminal.

3.  Zero   Ohm adjustment before testing so it will get accurate measured value.  Short 2 test leads together and adjust  0 Ω ADJ  knob till the pointer point at  0  Ohm mean it is  ready  to  test.

                                                              Zero   Ohm adjustment 

4.   Forward  bias  to  diode by connect  the black test lead  Anode terminal and the red test lead to Kathode  terminal  as  photo.   The black test lead will supply  positive voltage and the red test lead will supply negative voltage ( it  come from internal AA battery polarity ) so the diode will get forward bias.

                                                      Forward  bias  to  diode

5.    Read the measured value  ,  forward  bias case.    

LV scale ( 0-3) as above photo diode has  forward voltage drop   =  0.7V  

LI scale (0-15) as above photo diode has  forward current    =  12.5mA 

6.   Reverse   bias  to  diode by connect  the black test lead  Kathode  terminal and the red test lead to Anode  terminal  as  photo below.

                                                Reverse   bias  connection  to  diode 

7.    Read the measured value  ,  reverse  bias case.    

LI scale (0-15) as above photo diode has  reverse  current    =  0 mA 

As  reverse current of small and medium diode is very small amount  micro amp ( such as  5.0uA) so the multimeter can  not sense  that  micro amp current   by setting  X 10 range.

8.   Check diode condition   and   summarize.

Good diode will get  forward  voltage drop  0.3-08V  when  forward bias testing.

Good diode will get 0mA ( very small amount uA) when  reverse bias testing.

Bad diode ( shorted )  will get  0 Ohm and  switch the test  leads still get 0 Ohm.

Bad diode ( Open )    will get  ∞  Ohm and  switch the test  leads  still get  ∞   Ohm.

Bad diode ( shorted )  , the pointer will point at  0 Ohm and switch the test  lead , it still get 0 Ohm.

Bad diode ( open )  , the pointer will point at  ∞   Ohm and switch the test  lead , it still get ∞   Ohm.

8    Important     Testing    electronic    device   on    this   blog . 

Testing  electronic device  IGBT testing SCR testing Triac Testing Check mosfet and more

Read   on   this   page.

https://www.testmultimeter.com/p/testing-electronic-device-igbt-testing.html

Read    more ....    all    of   testing   ,   list    of   the   article   here .

30 testing of electronic devices

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.

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

  Multimeter display for  internal  open  capacitor ( For demonstration purpose only )

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

   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.

                 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.

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.

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 )

Read    more   of      testing .

30 testing of electronic devices