What is it?

It's a 24bit MUX Analog Digital Converter board with SPI interface (3V3). You can sample multiple sensors at high resolution and quite fast. It has 8 bipolar or 16 unipolar inputs. There is also a Arduino library for it, check here or download it from the Arduino library manager. The actual resolution depends on the sampling rate chosen: 24bit is only at 1 sample per second, at 1000 you get around 21bit, just keep that in mind. Also it is a MUX-ADC, which means if you setup 1000 samples per second and use two channels you get 500 samples per second per channel.

Why did you make it?

It was developed for the brain-duino project to sample brainwaves from 2 channels 500 samples per second. The brain-duino uses an standard 16 MHz Arduino, which is quite slow so the maximum is 500 samples for 2 channels. So far I tested the board only with Arduino, in case you are interested for an additional development cost I am also willing to work on adding functionality to the Arduino library or develop a new library for platforms like Raspberry PI.

What makes it special?

There aren't many 24 bit breakout boards out there. The AD7173 is a low noise and high quality ADC. The board is small and compact, so it should be nice to integrate it into any project or product. In case you are interested for an additional development cost I am also willing to change to board layout according to your needs.