I would like to use a MAX31855K IC for amplifying K type thermocouple response. This alone seems rather straightforward, but I'm also considering connecting 2 or 3 thermocouples to one IC. I don't need high frequency (a measurement every 0.5s is enough) and I also don't need it to be super accurate. I'll be measuring high temperatures, in ranges of 300-600C (570-1100F) and I'm fine with accuracy of 10-15C in that range.
I found a project that uses ADG407 analogue multiplexer for that, which was described as a successful try.
Before I try this on my own, I would like to ask on what should I consider when looking for multiplexers for this project? Or even, is a multiplexer the right choice? There're multiple ways of routing signals. I could also probably use an analogue switch IC, or maybe even some kind of transistors?
Initially I was thinking that a really low Rdson (like a few ohms) would be a key, to not alter a signal, but on the second thought the current there is probably close to 0, so ADG407's 80 ohms sounds fine. Is there anything else to consider? Is there any Rdson level that would not be acceptable for my requirements?