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Glossary & Abbreviations
Specific conductance = conductivity at 25 °C—The ratio of the electric current density
to the electric field in a material. The ability of a fluid to conduct electricity. Specific
conductance is the inverse of electrical resistivity, corrected at 25 °C, since fluids conduct
more at higher temperatures.
Spot-checking—The collection of data using readings at irregular intervals.
Temperature—A measure of heat present in water. Aside from dissolved oxygen,
temperature is considered the single most important parameter. Knowledge of water
temperature is essential to the measurement of dissolved oxygen, conductivity (salinity),
pH, alkalinity, biological/biochemical oxygen (needed to meet the metabolic needs of
aerobic - requiring D.O. - organisms) and virtually every other water quality parameter.
Temperature controls metabolism (utilization of inorganic and organic matter for life
processes) of aquatic animals and plants. Temperature is largely responsible for
biochemical reactions and is one of the most important cues for beginning and ending of
spawning, migration, and many other phenomena.
Titration—A method of analyzing the composition of a solution by adding known amounts
of standardized solution until a given reaction - color change, precipitation, or conductivity
change - is produced. Winkler titration (in calibration): A wet chemical method for
estimating the D.O. in water.
Tolerance—Refers to the maximum difference between the true value of a parameter and
the actual "operator-acceptable" reading. Usually used as a synonym for accuracy.
Total dissolved gas (TDG)—The amount of gaseous compounds dissolved in a liquid.
Total dissolved solids (TDS)—The amount of materials in a body of water that are
dissolved or too small to be filtered. These solids include ions, which are important to the
internal water balance in aquatic organisms. The amount of substances (calculated in
Kg/l) dissolved in one liter of water. A measure primarily of alkaline earth metals and their
salts dissolved or in very fine suspension. It provides information regarding the potential
buffering capacity of water, water hardness, and the potential lethality of toxins. The
concentration of dissolved solids affects osmoregulation (salt balancing) and is often a cue
for migration and spawning. TDS concentration affects the buoyancy of fish eggs and
other organisms.
Transducer—Any device or element which converts an input signal into an output signal
of a different form (ex: doorbell, microphone). The depth or vented level transducer.
Turbidity—The measure of the clarity of a liquid by using colorimetric scales. It is also the
expression of the optical property that causes a light to be scattered and absorbed rather
than transmitted in straight lines through a sample. Turbidity is the opposite of clarity (ITM)
A measure of the opacity or translucence of water. The main objective is to determine the
scattering of light by particles of a body of water and report that scattering in some unit of
measurement, usually nephelometric turbidity units (or NTU) based on a primary turbidity
standard called formazin. Turbidity is caused by plankton (both animal and plant), clay,
suspended clay, silt, etc. Although these substances impart color, color resulting from
turbidity is referred to as "apparent color" and should not be confused with true color
(resulting from dissolved substances). Apparent color can also result from overshading by
vegetation or substrate (bottom material) color.
Vented depth—(ITM) The multiprobe transducer measuring depth from 0 to 10 meters.
(See: Depth)
Zero—(ITM) A system's "zero" is an anchor point set either temporarily by calibration or
permanently by design. This point can easily be established either electronically or by
using laboratory standards. (Also see: Slope).
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