That chip is an A/D converter, but it has an "SPI" interface. That is a bit of a different animal than you asked for in your original post (SDI-12). If SPI is what you want then fine, but if your original posts lack the necessary precision you should not be surprised at the hit or miss quality of the responses.Thanks for coming back.
I found the MCP3202-CI/P that claims 12 bit dual channel serial output.
I will look at this one.