Technically, temperature is a measure of the energy of the molecules comprising a substance.  For our purposes, it’s how hot or how cold a water body might be.  The Centigrade scale is used most often in studies of water.

pH Sensors

Eureka's pH sensor does not use a gell design but instead uses a refillable reference electrode which provides multiple years of field use without costly replacement. 


Conductivity is the ability of water to conduct electricity.  This conduction requires ions in the water to be charge carriers.  Pure water contains no ions (aside from the occasional rogue water molecule), and so is a very poor conductor of electricity.  But as water picks up chemical salts, those salts add ions to the water when they dissolve.  So as the ionic strength of the water rises, so does conductivity - the “saltier” the water, the higher the conductivity.

Optical Dissolved Oxygen

The Optical Disolved Oxygen (HDO) sensor has been used in the field for 4+ years with an incredible track record for accuracy, reliability and length of life. 


Turbidity is an indication of the amount of light that will pass through a column of water.  Clear waters have low turbidity; waters with high suspended solids have high turbidities.

Eureka offers a full line of fluorometers including chlorophyll a (blue), chlorophyll a (red), Blue-Green algae(freshwater & marine), rhodamine, optical brighteners, CDOM/FDOM, tryptophan, fluorescein dye, crude oil and refined oil. All Eureka fluorometers are based on the Turner Designs Cyclops-7 submersible fluorometer ( 

Ion-Selective Electrodes (ISE)

Ion-Selective Electrodes (ISE’s) are a class of sensors that respond to the presence of specific ions, such as sodium (Na+) or bromide (Br).  They are used in conjunction with a reference electrode, and report ion concentrations in mg/l.

Eureka offers ammonium, nitrate, chloride, sodium, calcium and bromide.

Total Dissolved Gas (TDG)

Total Dissolved Gas (TDG) is actually the sum of the partial pressures of all gases in a water sample.  Normally, the sum of gas partial pressures will be about one atmosphere (15 psi) for any water that is exposed to the atmosphere

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Ion-Selective Electrodes (ISE)