77
TROLL
9500
Operator’s Manual
0095110 rev. 007 01/09
Total Dissolved Solids (TDS)
A factor of 0.65 x specific conductance is used to estimate Total
Dissolved Solids (TDS). This was chosen for general applicability.
Remember that ions in solution will vary, and this general conversion
factor will not fit all situations exactly. Units: mg/L
Resistivity
The reciprocal of conductance is resistance. Resistivity is the resis-
tance times the cell constant. Resistivity is useful when monitoring
pure water. Units: Kohms cm
Salinity
Calculated from conductivity and temperature using the Practical
Salinity Scale adjusted for low salinities. Units: PSU (Practical Salinity
Units)
The original Practical Salinity Scale (1978) was considered valid for a
range of 2-42 PSU; “standard seawater” is defined as having a value
of exactly 35. In 1986, there was an adjustment to the scale for better
accuracy with low salinities. That adjusted scale is considered valid for
a range of 0-40 PSU. Above 2 PSU there is no significant difference
between the two scales. “Fresh” water would typically have values
below 1, and typically very close to 0.
USAGE RECOMMENDATIONS AND CAUTIONS
CONDUCTIVITY AND TEMPERATURE
Conductivity is a function of temperature. According to the EPA,
temperature variations and corrections represent the largest source
OFPOTENTIALERRORINCONDUCTIVITYMEASUREMENTS!½#CHANGEIN
temperature can cause a 0.2% change in conductivity.
3PECIlCCONDUCTANCEISTHECONDUCTIVITYOFASUBSTANCEAT½#AND
MEASUREMENTSAREUSUALLYSTANDARDIZEDTO½#WHENITISNECESSARY
to compare data. When the temperature of a sample and its conduc-
tivity at that temperature are known, the software can extrapolate the
CONDUCTIVITYTO½#
sensor
removal
tool
SENSOR CARE AND HANDLING
SENSOR REMOVAL
Position the yoke of the sensor removal tool at the point
where the sensor enters the sensor block and pry the
sensor upward.
MAINTENANCE/INSPECTION/CLEANING
#HECKTHESENSORFORFOULINGOFTHEELECTRODES)FNECESSARYmUSHTHE
sensor with water, or swish in a mild detergent solution and rinse with
tap water. A swab or soft-bristle brush may be gently used to clean
the electrodes. Remember that the electrodes are made of graphite,
which is soft and easily damaged.
STORAGE
Store the sensor dry.
REFERENCES
Eaton, A.D., L.S. Clesceri, E.W. Rice, and A.E. Greenberg, eds.,
Standard Methods for the Examination of Water and Wastewater,
21st edition, Washington, D.C.: American Public Health Associa-
tion, American Water Works Association, and Water Environment
Federation, 2005. Section 2510, Conductivity. Section 2520 B,
Salinity - Electrical Conductivity Method.
EPA, Methods for Chemical Analysis of Water and Wastes,
EPA/600/4-79-020, revised March 1983. Method 120.1, Conduc-
tance, Specific Conductance. Approved at 40 CFR Part 136.
The International Association for Physical Science of the Ocean
(IAPSO) Standard Seawater manufactured by Ocean Scientific In-
ternational is available in North America from Guildline Instruments
Inc. in Lake Mary, Florida.
SECTION 12: CONDUCTIVITY