I am measuring several 5kOhm NTCs with 3x 34901A 20 Channel Multiplexer with a 34970A.
Can I have problems if I connect one side of all sensors together?
I have tested it with 2 sensors and it worked, but is it a reliable solution?
This works fine as long as you are careful to be sure that there are no extraneous voltages on the NTC leads. In other words, make sure the NTC leads don't make electrical connections to any points where there are significant voltage differences, because when you connect this way eacn NTC no longer has a floating connection to the DMM. You are vulerable to ground loop problems, but as long as you are carefully with the wiring, this should work without problems.