30
MW170 Bench Meter
9.3. MEASUREMENT
MW170
supports three seawater salinity scales:
y
Practical Salinity Units (PSU)
y
Natural seawater (g/L)
y
Percentage NaCl (%NaCl)
Press RANGE/
to select between salinity scales. Verify that the required scale is
configured in SETUP.
Note: These units are for determining salinity and they refer to general use of saltwater.
Practical salinity and natural seawater require a conductivity calibration. %NaCl
requires calibration in MA9066 standard.
PSU – Practical Salinity Units
The practical salinity (S) of seawater relates the ratio of electrical conductivity of a
seawater sample at 15 °C and 1 atmosphere to a potassium chloride solution (KCl) with a
mass of 32.4356 g/Kg water at the same temperature and pressure.
The ratio is equal to 1, and S=35. The practical salinity scale may be applied to values to
through 42.00 PSU at temperatures between -2 to 35 °C.
Salinity of a sample in practical salinity units (PSU) is calculated using the following
formula: