Operational Guide 31
Note:
• These are for determining salinity as they relate to general oceanographic
use.
• Practical salinity and the Natural Seawater require a conductivity
calibration.
• NaCl % requires a calibration in HI 70371 standard.
PSU - Practical Salinity Units
The practical salinity (S) of seawater relates the ratio of electrical conductivity
of a normal seawater sample at 15 ºC and 1 atmosphere to a potassium chloride
solution (KCl) with a mass of 32.4356 g/Kg water at the same temperature and
pressure.
Under these conditions the ratio is equal to 1, and S=35. The practical salinity
scale may be applied to values to through 42 PSU at temperatures between -2
to 35 ºC.
According to the de nition, salinity of a sample in PSU (practical salinity units) is
calculated using the following formula:
NaCl % Percent Scale
The NaCl % scale is an older salinity scale used for seawater salinity. In this scale
100% salinity is equivalent to roughly 10% solids. High percentages were made
by evaporation. To display NaCl in % units, enter SETUP and select NaCl% unit.
Press the RANGE key until “NaCl%” is displayed on the LCD. The instrument will
display the NaCl% reading on the rst LCD line and the temperature reading on
the second LCD line.
Salinity
Measurements
f(t)=
T-15
1 + 0.0162•(t-15)
a
0
= 0.008
a
1
= -0.1692
a
2
= 25.3851
a
3
= 14.0941
a
4
= -7.0261
a
5
= 2.7081
b
0
= 0.0005
b
1
= -0.0056
b
2
= -0.0066
b
3
= -0.0375
b
4
= 0.0636
b
5
= -0.01442
c
0
= 0.008
c
1
= 0.0005
X = 400R
T
Y = 100R
T
R
T
- ratio of sample conductivity to standard conductivity at Temp =(T)
C
T
(sample) - uncompensated conductivity at T ºC;
C(35,15) =42.914µS/cm - the corresponding conductivity of KCI solution
containing a mass of 32.4356 g KCl/1 Kg solution
r
T
- Temperature compensation polynomial
To Next Page
Loading...
Need help?
General
