use of multiple 3208 a/d chips

//free pin mode declaration AH_MCP320x(int CS_pin, int DOUT_pin, int DIN_pin, int CLK_pin)

//SPI mode declaration AH_MCP320x(int CS_pin)

//read channel ADC value int readCH(int CHANNEL)

My application requires 16 ch of 12bit a/d. I have 2 mcp3208 with independent CS signals connected to the arduino pins 9, 10.

I am using the AH_MCP320x.h lib and it works well.

I assume I would use the "free definition version" below to use a different CS.

AH_MCP320x ADC_SPI(10); //Object definition with D10 as CS, other pins are defined by spi interface (faster mode).

//AH_MCP320x ADC_pin(10,11,12,13); //Object definition with free definition of communication pins (slower mode).

However aren't these meant to be used ahead of the setup loop?

That's the problem with libraries, got to figure out what they're doing when you want to use them with more than one instance. In the time spent doing that, you could just as easily write two for loops to cycle thru each part to perform the 16 conversions and get the data back.