Abstract：Instrument is a tool to obtain information and it is a mean of understanding the world. It is a specific system or device. Its basic function is extension, expansion, supplement or replacing with people’s hearing, visual, tactile and other organ functions. With the continuous development of science and technology, human society has entered into the information age, the stronger the dependence of instrument, the higher it demands.
This article designs a automatically shift voltage meter，the control system adopts a single-chip AT89S52 of Atmel Corporation and the ADC0809 used as the main A / D converter hardware. It achieves the functions that automatic shift through the combination of 74LS138 chips and relay .The system’s digital voltage meter circuit is simple, fewer components are used , low in cost and regulation work can be achieved automatically. It can measure 0 - 200V input voltage value and display the measurement results on 8 LED digital tube.
The simulation results show that the largest range is 200V, the error is less than 3% and can be automatically convert voltage range in accordance with the actual size of the voltage.
Key words: Instrumentation; Automatic Power Shift; Digital Voltage Meter; Error
