3. Digital oscilloscope

Increasingly powerful microcontrollers make a basic digital oscilloscope relatively easy to build. If you are going to build a PC based digital oscilloscope, you basically have two options. You can just design a simple voltage divider with two resistors to adapt the input voltage range to the line input voltage range, or you can use an USB capable microcontroller with A/D converter to capture signals. PIC18F24J50 has a 10-bit A/D converter with 10 inputs multiplexor, so it can monitor at most 10 analog input channels in time multiplex mode. The maximum sampling rate is about 100 kHz, so you would be better off with PC inbuilt sound chip A/D converter that goes up to 192 KHz. However, a PC inbuilt sound chip’s line input is limited to AC signals and cannot accurately determine signal level. This is because of preamplifier circuitry that is adapted for audio signals. PIC18F24J50 offers a bare A/D converter that can also measure DC signals. We are going to explore both options.