Saturday, February 20, 2021

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.

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

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

current tester
                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.

current measurement
                                   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.

current measurement
       Multimeter series connection with simple circuit  to demonstrate  current testing.

current measurement

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.

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

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

Test  Amp with  multimeter
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