Abstract: In circuit design it is often needed to adjust the resistance of the resistor, the traditional resistance
box has the disadvantages of small scale range, low resolution resistance, large volume, inconvenient and
others. Therefore, it is necessary to design a digital resistance box that has wide range of resistance, high
resolution resistance. The main purpose is to research and produce a digital active resistance box, which has
analog active resistance hardware circuit, and is controlled by ARM7 series microcontroller LPC2138
system. The active resistance box uses a matrix keyboard and a LCD(Liquid Crystal Display) liquid crystal
screen as a human computer interaction device to realize the digital setting and synchronous display of the
resistance value of the device. The experimental data show that the resistance range of the digital active
resistance box is 10. 01 Ω~ 10. 01 MΩ and the accuracy is ±0. 46% . It can be widely used in electronic
circuits.

Key words: wide range,  digital resistance box, high precision