I have an Arduino project which takes three variable voltage inputs (in the range 0.43V to 0.63V) to a 4051 multiplexer (FAIRCHILD SEMICONDUCTOR CD4051BCN). Each input is selected sequentially and passed through an OpAmp to the Arduino and on to the PC for logging and analysis. DC5V is taken from the Arduino.
I can control the multiplexer input voltages fairly accurately for testing purposes with a variable resistance and multimeter, also I can test the OpAmp is working ok and stable.
My problem is that the output from the multiplexer is hopelessly unstable and varies by +/- 20% or more from the input voltage and does not stabilise over time.
I have tried change the sampling rate and allowing more time for the output to settle before reading it - but no good!
As an electronics newbie I may have picked the wrong multiplexer - there seems to be a load of products available but not clear to me which is best for my application.
Any insight or guidance appreciated.