How to select analog switch or analog multiplexer

when i have started designing analog and digital circuits some times i had a requirement of performing multiplexing of analog channels.

Let us take an example:
suppose you have 4 different types of thermo couples placed at some place where there will be always temperature variation what do you perform to capture these signals is( as these signals are of very low AC voltage some thing like noise) you should have a means to filter them and pass them on to analog multiplexer.

Now when ever we try to select an analog multiplexer we need to consider the following things, what type of analog multiplexer it is whether single ended or differential multiplexer.

Second thing what we need to consider is the what is the output capacitance of the multipexer. Let me explain why do we need to find out the output capacitance of the multiplexer. Since we will be selecting each channel in the order we get the select bits from our microprocessor or FPGA by the time the channel changes the voltage of other channel might stand there as parasitic capacitance.

so to avoid that we will select a multiplexer with low output capacitance.
Now coming to the selection other factor we need to consider is the impedance of the mux. it should be as low as possible for better effective operation.

usually we need to use some kinds of buffers after multiplexer so that mux wont be loaded and that buffer will supply necessary source current to the output circuit.