1. Sensor: It will provide input signal, voltage or current signal to digital display meter.
2. Amplifier: It will amplify the input voltage or current signal.
3. A/D converter: Namely, the module converter, it is the core of digital instrument. Its role is to convert the continuous analog voltage signal into a discrete digital signal, and display measurement results in digital form.
4. Linearizer: Usually the sensors have nonlinear function relation, its function is to eliminate nonlinear error.
5. Register and Display Register and digital display the output signal of A/D converter.
6. Control logic circuit:  It is used to control the whole machine and to coordinate various parts work.