You can use a carrier board to hold the sensor modules and provide all the connections. Or you can use your own custom PCB.
Conductivity is used to measure drinking water quality, hydroponic nutrient levels, and salinity.

Isolation

Probes

pH is used to measure drinking water quality, hydroponics, and pools.

Isolation

Probes

ORP is used to measure oxidative potential of water. It can be used as a proxy measurement of pool disinfectant levels.

Isolation

Probes

Water temperature is required for accurate conductivity and pH measurements.

Power

Probes

The following are all the components needed. Each link will open in a new window and provide more detailed information, allow you to add it to the cart, and checkout.