Recently I needed to actually “see” a current waveform in the 100 uA to 5 mA range with at least a couple MHz bandwidth. This extremely expensive probe would have been perfect, but instead I built something similar for about $30 using the amazing Analog Devices AD8428 amplifier.
Rather than buying an extremely costly o-scope that would measure microamp signals in high resolution, Paul over at Dorkbot PDX built this circuit to feed precision data to his own bench equipment. But he has some idea of how that high-end equipment does things, and so he just built this circuit to feed precision data to his own bench equipment.
The oscilloscope screenshot in Paul’s post is really impressive. Using two 1 Ohm resistors in parallel on the microcontroller’s power line he’s able to monitor the chip in slow startup mode. It begins at 120 microamps and the graph captures the point at which the oscillator starts running and when the system clock is connected to it.
(Credit: Mike Szczys of HaD)
I found this to be a fascinating read – both on Mike’s post as well as the source. Take a look for yourself at the links below!
(via Hackaday, Dorkbot PDX)