Thermo Scientific Orion Star A320 Series Manual page 43

Chapter 3 Meter Setup Menus
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Salinity Type Setting
Orion Star A322 conductivity meters, Orion Star A325 pH/conductivity meters and Orion Star
A329 pH/ISE/conductivity/RDO/DO meters offer two salinity types: practical salinity and natural
sea water. Practical salinity measurements are based on relating the sample measurement to
the reading of a standard potassium chloride (KCl) solution at 15 °C. Orion Star A320 series
conductivity meters will automatically temperature compensate and report the expected
practical salinity result as practical salinity units (psu) at 15 °C when using a conductivity sensor
with built-in temperature. Natural sea water measurements use a historic convention known as
UNESCO 1966 and Orion Star A320 series conductivity meters will report the expected natural
sea water result as parts per thousand (ppt).
TDS Factor Setting
Orion Star A322 conductivity meters, Orion Star A325 pH/conductivity meters and Orion Star
A329 pH/ISE/conductivity/RDO/DO meters measure TDS as the total amount of dissolved
inorganic material in a solution. The dissolved inorganic material carries a current that is
measured by the conductivity sensor. Since there is a direct relationship between conductivity
and TDS, conductivity readings are used to estimate the presence of inorganic material using
the TDS factor entered in the setup menu.
The standard method of determining TDS involves evaporating a sample to dryness at 180 °C
and weighing the residue. The TDS factor is calculated by taking the residue weight and
dividing it by the sample conductivity. Subsequent conductivity readings are multiplied by the
TDS factor to determine the TDS value of the sample.
Cell Type Setting
Orion Star A322 conductivity meters, Orion Star A325 pH/conductivity meters and Orion Star
A329 pH/ISE/conductivity/RDO/DO meters accept 2-cell and 4-cell conductivity sensors and
allows the type of conductivity sensor to be set as Standard (most conductivity sensors) or USP
(for the ultra pure water conductivity sensor, Catalog Number 013016MD, when disabling
temperature compensation).
Thermo Scientific Orion Star A320 Series Portable Meter User Manual 43
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