Help understanding sensor placement on multiplexing schematic

Working off of this schematic:

You could call me an extremely novice engineer. I know that wiring something up would typically (always?) have a ground or a negative end to the circuit, so this confuses me when looking at the schematic for each cluster of sensors.

It looks like each sensor has one wire/connection to a pin on the multiplexing chip, giving each chip 16 sensors. So if I imagine this, I see a wire going from the chip to one end on each sensor (LDR or Light Sensor or whatever you want to call, it in my case)… so does the other end of the sensor go to nothing?

I threw together an illustration of my confusion:

Each analog multiplexer connects one of 16 pins to an Arduino analog input. In the diagram each of those 16 pins has a pull-up resistor. Those are only necessary if your "sensor" is a variable resistor: LDR for light, Thermistor for temperature, PDR for pressure... In those cases the other end of the sensor goes to Ground and the sensor/resistor combination acts as a voltage divider.

If your 'sensor' is a potentiometer you should leave out the pull-up resistor. Connect the ends of the pot. to +5 and Ground. Connect the wiper of the pot. to the input pin.

If your sensor is some other form of voltage source (0 to 5 volts) you should also leave out the pull-up resistor.

hi... if i want to use capacitive sensor here , how do i use them. Is there any requirement of external voltage source. your earlier help will be apreciated.

if i want to use capacitive sensor here

I would forget it. The capacitive sensor idea is not a very reliable thing to do, it is even less reliable when using a multiplexer on the input. This is because :- 1) It relies on a very high impedance input. 2) Multiplexers do not work well if at all with high impedance inputs, there is too much cross talk between the channels.