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I'm trying to connect 36 analog voltage sensors to the 6 analog pins of an Arduino Uno and cannot figure out the simplest way to go about it, given that I need to be able to accurately read a voltage that stays within 2.6 and 3.6 volts.

This is the sensor, 10Pcs Voltage Tester Sensor Detection Module DC 0-25V for Arduino Robot Car USA

Voltage Tester Sensor Detection Module

and they are measuriing 36 of these CALB 100 Ah CA Series Lithium Iron Phosphate Battery

ALB 100 Ah CA Series Lithium Iron Phosphate Battery

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    \$\begingroup\$ How are you planning on connecting your batteries? Those "voltage sensors" are little more than two $0.001 resistors configured as a 5:1 resistor divider. If you put all your batteries in series, then you will exceed the voltage ratings of your Arduino ADC. \$\endgroup\$ – W5VO Jun 13 at 17:32
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If you want to spread out the multiplexed outputs among the six inputs, what comes to mind is six 8:1 analog multiplexers, one for each Arduino input. Two inputs are unused on each chip.

To select the best part, you need to know the output impedances of the sources, the input impedances on the Arduino inputs, and the maximum frequency of interest in the signals being monitored. All analog switches have an internal resistance or impedance when a channel is "on", and that impedance is not constant; it changes based on the signal voltage. Look at the CD4051 datasheet for a plot of this. Ideally you want that resistance to be very small compared to the sum of the source and destination impedances in the complete circuit.

Now that you've added information about the battery, the last questions are the input impedance of the Arduino input and the desired accuracy.

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