Mux using 4051

Hello:

I have 4 or more analog sensors that each have outputs ranging +/- 2000mV. Presently planning on using a 4051 MUX.

  1. Since the signal can be negative do I need to offset the signal to a positive voltage before sending to the Arduin’s AO pin? If so, any recos on how?

  2. . Since the signal can be negative do I need to supply the 4051 with a bipolar power supply?

Thanks

I have 4 or more analog sensors that each have outputs ranging +/- 2000mV.

So how are they powered? Do you have a split rail supply? If so what is it. If you can connect the -ve of your supply to the Arduino ground the signals will all be positave with regard to the Arduino.

However you are very scant on detailes, you don’t even seem to know how many sensors you have.
What kind of output do these sensors produce, AC or DC?
Please post a link to the sensors and a schematic of how you are powering them.

Thank you for your reply.

For ease of discussion let me reduce the sensors down to two for now. One of the sensor reads pH of pool water and the other reads the ORP of pool water. These two sensors do not need an external supply. The signals generated are DC, +/- 2000mV. For the pH sensor every +59.2 mV represents a pH unit below 7.0 indicating an acidic liquid and similarly every -59.2mV represents a pH unit above 7.0.

The ORP sensor output is a standalone value where +850mV indicates an acceptable value for pool water quality.

A pH probe has a very high impedance so it needs to be used with a buffer amplifier. The Arduino can only measure positive voltages and so the signal needs a DC shift before measuring can be done. This also can be done with an amplifier.
So you need something like the circuit shown here pH measurement

Although that link shows construction on a Solderless bread board which I would not recommend for a permanent layout.

Once the signal has been buffered and DC shifted it can be multiplexed by a 4051 just like any other signal.