Tuesday, November 30, 2021



POTENTIOMETER ( small)   and  RHEOSTAT  ( big )

Potentiometer  is  a   variable resistor .  It   use  to  adjust  signal  and  low current on electronics  circuit.   It   has   3  terminals.   If   you want  a variable resistor that can handle more current,  you may   looking  for   rheostat.



We will     name as terminal 1 and  2 and 3 when measure .

Step to   check   Potentiometer  and  rheostat.
1.  Read   the resistance  value   that   marks   on  potentiometer  or   rheostat.

For example  this potentiometer  has  100K ohm  resistance.

This potentiometer below  has  10K ohm resistance.


2.  Set   the  rotary switch  of  multimeter  to   resistor test  function.
3.  Connect   the test leads   to  terminal 1 and 3  as shown on   photo.  Then read the measured value on multimeter.   The  measured value  should  be closest to  the resistance value on marking.
For exsample below  the potentiometer  is  100K ohm  and  multimeter get  measured value   as  100K ohm so   this is the good potentiometer.

Test resistor

4.   Connect   the test leads  to  terminal 1 and 2  as shown on  photo.  when  adjusting  the resistance by rotate potentiometer's  knob  the measured  value   should vary ,  you have to rotate the knob  clockwise and  counter-clockwise  ,   the measured  value should vary from  low resistance value increase to high resistance  value ,  from  high resistance value decrease   to low  resistance value ,  depend on knob's rotation.   The good  potentiometer should vary its resistance when  rotating .  In case of it is a damage or not good one  ( Bad potentiometer )  , resistance value will not vary when rotating   the knob.

Test  resistor
Connect   the test    leads  to  terminal 1 and 2 and  read  the measured   value.

5.   Connect   the test leads   to  terminal 2 and 3  as shown on  photo and  check likewise  as  step 4.
Test  resistor
Connect   the test leads  to  terminal 2 and 3  and   read  the measured   value.

Rheostat  has  3 terminals   as   potentiometer  also   it  has  the same step  to check.
Measurement   between  terminal 1 and  3  should get  measured  value as  it's  marking.  When checking   terminal 1 and 2  ,   terminal 2 and 3  , the resistance value must vary when you rotate the  rheostat's knob.

Connect test leads to terminal 1 and  3  , get measured resistance as it  marking.

Test  resistor
Connect test leads to terminal 1 and  2  ,  rotate the  knob to test resistance vary.

Test  resistor
Connect test leads to terminal 2 and  3  ,  rotate the  knob to test resistance vary.