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
- 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.
- These instruments have a high impedance, this input resistance is typically up to 10 MΩ and their input capacitance is typically 40pF.
- The high input impedance results in an instrument which almost never loads the circuit in which it has been introduced.
- Due to the complete absence of the moving mechanical parts, these instruments have a zero operational power consumption.
- 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.
- Digital instruments have a high accuracy due to the above characteristics, as high as ±0.005% of the reading.
- Digital instruments are both overanged of automatically ranged.
- These instruments are calibrated internally with the help of an internal standard stabilized source.
- Digital voltmeters cab be designed to measure voltages ranging from 1V to 1000V.
