A water quality meter directly measures many different characteristics of the water using different sensors. The R/V Rutgers has sensor that measure conductivity, temperature, dissolved oxygen, and pH.
Why we collect this data
These measurements provide us with basic information about the ecosystem, including health and habitability, as well as providing insight into the source of the water (freshwater from runoff or saltier water from tides). The conductivity and temperature can also be used to determine density. The density differences between different masses of water can cause currents.
By measuring the dissolved oxygen (DO) we can get information about the water quality. Like us, many organisms require oxygen for respiration to live. Thus, if the (DO) levels drop too low, organisms cannot survive.
The pH determines the amount of gas, nutrients, and heavy metals that can be dissolved in the water and the amount that can be used by organisms in the water.
How it works
The YSI determines conductivity by measuring how well the water conducts an electric current. This information can then be used to determine salinity.
Temperature is determined using a thermistor, which measures temperature based upon changes to the electrical resistance of a metal.
The dissolved oxygen sensor measures the how long certain dyes in the sensor emit light (luminesce) after reacting with the oxygen. The more oxygen, the longer the luminescence.
This probe measures the voltage, which can then be used to calculate the hydrogen ion (H+).
Image credit: https://www.ysi.com/prodss