Variable range 1.2~1000V point mode sound and light voltmeter circuit

The circuit is shown in the figure. It is composed of LM3914 as the core. LM3914 is a linear scale device. Its 10 outputs can directly drive light-emitting diode (LED) devices. The number of lit LEDs directly indicates the volt value of the input voltage. This principle can be used to easily make a 0-1.2V linear voltmeter with 10 LED scales. Figure (a) is the internal circuit of LM3914 and the external connection of the 0~1.2V linear voltmeter; Figure (b) is the 1.2~1000V voltmeter circuit composed of LM3914.