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Digital Multimeter
April 15, 2018
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Digital Multi-meter is used to measure various electrical parameter like voltage, current, resistance, capacitance and it also used to test connectivity,  transistor, waveform, etc and show value on digital display. Digital Multi-meter is one of the basic tool of electrical and electronics engineer which they used to design electrical and electronics circuit. It is also used by various electrical mechanic in repairing process.

Depending on price the variety and functionality may be varied. One of basic multi-meter is DT830D Digital Multi-meter which you can buy from online or offline store at cost of approx. Rs.300.

DT830D Digital Multi-meter is capable of measuring

  1. DC voltage (200 mili-volt to 1000 volt) DC voltage
  2. AC voltage (200 volt to 750 volt) ac voltage
  3. Current (2000 micro-ampere to 200 mili-ampere) or (10 ampere) 
  4. Resistance (200 ohm to 2000 K ohm) 

DT830D Digital Multi-meter is capable of testing

  1. LED (Light Emitting Diode)
  2. Wire Continuity
  3. Transistor (NPN and PNP)
  4. Wave form  (Required oscilloscope price above Rs. 11,000)

Voltage is define as the potential difference between two points. It is denoted by "V" and unit is volt. Voltage are of two type AC(Alternating Current ) voltage and DC (Direct Current)voltage.

Batteries and DC generator  provide DC current and voltage on other hand Alternator or AC generator provide AC current and voltage.

Procedure to measure DC voltage 

  1. Put the range switch (Dial in middle) pointer to the maximum DC voltage.
  2. There are two probe Black (put in common jack) and Red (put it in V Ω mA jack) Common and voltage jack
  3. Now, touch the probe pointer to positive and negative potential in the circuit. It will display the value on display.

 

Note: If it shows the positive value then Red probe is at positive potential. If is downs negative value then Red probe is at negative potential. In this condition changing of probe position will correct your reading. So, by this you can also know which  is positive or negative terminal.

 

Procedure to measure AC voltage 

  1. Put the range switch (Dial in middle) pointer to the maximum AC voltage.
  2. There are two probe Black (put in common jack) and Red (put it in V Ω mA jack)
  3. Now, touch the probe pointer to positive and ground potential in the circuit. It will display the value on display.

Current is define as the flow of charge in the wire. It unit is ampere and denoted by "A". To measure current you should connect your multi-meter in series.

Procedure to measure AC voltage 

  1. If current is above 200 mili-ampere then put the range switch to 10 A otherwise put it in 200 mili-ampere to 2000 micro-ampere.
  2. If current is above 200 mili-ampere put the red probe in 10A jack and black probe in common jack otherwise put the red probe in V Ω mA jack and black probe in common jack.
  3. Connect the multi-meter in series.

 

Resistance is the property of the material which opposes the flow of current throw it. It unit is ohm and denoted by symbol "Ω".

 

Procedure to measure resistance 

  1. Put range switch in resistance area.
  2. Put black probe in common jack and red probe in V Ω mA.
  3. Touch one of the terminal of resistor with red probe and other terminal with black probe. Resistance value will be display.

Note : Calculate fixed resistance value using formula.

Procedure to test LED (Light emitting Diode)

  1. Put the range switch pointer at Led and connectivity
  2. Connect black probe in common jack and red probe in V Ω mA jack.
  3. Touch red probe to P-terminal of LED and Red probe of N-terminal of LED
  4. LED will glow. 

Note: LED will glow only in forward bias not in reverse bias.

Procedure of check wire continuity 

  1. Put the range switch pointer at Led and connectivity
  2. Connect black probe in common jack and red probe in V Ω mA jack.
  3. Touch red probe to one end of wire in the circuit and black probe to other end of wire. 
  4. If continuity is OK. Then it will make beep sound.

Procedure to check transistor

  1. Put the range switch pointer at hFE mode
  2. Connect black probe to common jack and red probe to V Ω mA jack.
  3. You should now what type of transistor you have NPN or PNP.
  4. Connect the transistor Base, Collector and Emitter to the respective hole here  NPN and PNP tester
  5. If it show hFE value then your transistor is okay.

 

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