The basic difference between Analog & Digital Instrument is given below.

S.No. Aspects Analog Instrument Digital Instrument
 1.  Information form  As the position of pointer on a dial/scale  As a number
2.   Possibility of human error  Exists Does not exist 
3.   Best possible accuracy  0.25%  +0.005% or greater
4.   Resolution  one in several hundreds  one part in several hundred thousand
5.   Presence of moving parts  moving part involved  No moving part
6.   Construction simple, direct reading type, can perform in unfavourable conditions   involves electronics, proper environmental conditions are required
7.   Rate of change of parameter  By seeing needle movement  No knowledge of change
8.   Time required to observe reading  If exact reading is required operator takes more time to guess the approximate tenths of small division  Very fast
9.   Auxiliary power requirement  No requirement of auxiliary power.  Require auxiliary source of power
10.  Mobility Can be portable Staionary
11.  Examples speedometer of an automobile, fuel gauge, voltmeter, ammeter, thermometer, etc. Digital ammeters, voltmeters, etc.

Advantages of Digital Instruments over Analog Instruments

  1. The output of these instruments in the BCD format and hence it can be directly restored to a secondary storage device or processed by a computer.
  2. These instruments have a high impedance, this input resistance is typically up to 10 MΩ and their input capacitance is typically 40pF.
  3. The high input impedance results in an instrument which almost never loads the circuit in which it has been introduced.
  4. Due to the complete absence of the moving mechanical parts, these instruments have a zero operational power consumption.
  5. Digital instruments high resolution and the digital voltmeter can be designed to measure voltage as is called as 1μV on its 1V range or 1mV on its 1000V range.
  6. Digital instruments have a high accuracy due to the above characteristics, as high as ±0.005% of the reading.
  7. Digital instruments are both overanged of automatically ranged.
  8. These instruments are calibrated internally with the help of an internal standard stabilized source.
  9. Digital voltmeters cab be designed to measure voltages ranging from 1V to 1000V.
Difference between Analog & Digital Instrument

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