Arduino enthusiasts with an interest in analogue electronics, and more specifically the field of measurement and test will soon outgrow the accuracy of the Arduino's onboard ADCs. At that point you can select from seemingly hundreds of external ADC parts and several interfaces. To help simplify this process Kerry Wong has created a great library for the Microchip MCP3903 - which in Kerry's words
... features six synchronous sampling differential channels which can be programmed to sample between 16 bit and 24 bit accuracy, the gain for each channel can also be programmatically set from 1 up to 32. It also has an internal low tempco (5ppm/°C) voltage reference, making MCP3903 an excellent choice for digitizing small differential signals from various sensors
Kerry's library is easy to use, and includes reset, gain adjustment and functions to retrieve values from the ADC. For more information, download links and heaps of other interesting articles check out Kerry's website. And for more, we're on facebook, Google+, and twitter - so follow us for news and product updates as well.