Thermo Scientific Russell RL060C, Руководство пользователя

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Thermo Scientific Russell RL060C Conductivity Meter User Guide 6
If .the .plates .are .close .and .the .electric .field .is .strong, .ions .will .reach .the .plates .more .
quickly .than .if .the .plates .are .far .apart .and .the .electric .field .is .weak . .By .using .cells .with .
defined .plate .areas .and .separation .distances, .it .is .possible .to .standardize .or .specify .
conductance .measurements . .
Thus .derives .the .term .specific .conductance .or .conductivity . .
The .relationship .between .conductance .and .specific .conductivity .is: .
Specific .Conductivity, .(SC) . .= .(Conductance) .(cell .constant, .k) .
=siemens* .cm/cm
2 .
= .siemens/cm
Since .the .basic .unit .of .electrical .resistance .is .the .ohm, .and .conductance .is .the .
reciprocal .of .resistance, .the .basic .unit .of .conductance .was .originally .designated .a .
“mho” .– .ohm .spelled .backwards .– .however, .this .term .has .been .replace .by .the .term .
“siemen” . .Conductivity .measurements .are .reported .as .Siemens/cm, .since .the .value .
is .measured .between .opposite .faces .of .a .cell .of .a .known .cubic .configuration . .With .
most .aqueous .solutions, .conductivity .quantities .are .most .frequently .measured .in .
microSiemens .per .cm .(μS/cm) .or .milliSiemens .per .cm .(mS/cm) . .
The .salinity .value .which .ranges .from .2 .to .42 .is .a .measure .of .all .salts, .not .just .sodium .
chloride . .This .scale .was .originally .devised .for .seawater, .and .is .based .on .seawater .at . .
15 .°C .having .a .conductivity .equivalent .to .that .of .a .potassium .chloride .solution .of .a .
known .concentration . .This .solution .(0 .44 .molar) .is .defined .as .having .a .salinity .of . .
35 .ppt . .
The .total .dissolved .solids .scale .approximate .the .ppm .TDS .in .surface .waters .by .
multiplying .the .conductivity .of .a .sample .by .a .factor, .0 .66 . .
Some .users .prefer .the .use .of .resistivity .units .to .describe .their .water, .particularly .
where .high .purity .water .is .involved . .The .unit .most .often .used .to .describe .resistivity .is .
megohm-cm, .which .are .simply .the .reciprocal .of .conductivity .(μS/cm) . .The .chart .below .
shows .the .relationship .between .these .units . .