Linearity Pack

 Salinometer calibration for measurement of oceanic samples is traditionally carried out using IAPSO Standard Seawater (salinity = 35). For measurement of samples of higher and lower salinity, OSIL produce standards at salinities of 10, 30 and 38. Salinometer linearity checks provide a useful diagnostic tool in assessing the function of a salinometer. Offset values can be used to improve the accuracy of measurements made away from 35 salinity. A large offset away from the 35 salinity point can be indicative of electronics misalignment, cell ageing or temperature bath malfunction.

A typical proceedure for linearity correction would be:

1) Standardise the salinometer with P-series Normal Standard Seawater (Salinity 35)

2) Measure the salinities for 38H-series, 30L-series and 10L-series Standard Seawaters

3) Calculate the difference between the measured value and the label value for each of these standards
i.e. measured value-label value = salinometer offset

4) Plot a graph of offset at each salinity ( a linearity curve).

5) Use the plotted offset data to correct salinity measurements away from salinity 35
e.g. at salinity 10 the offset is -0.004 in salinity, therefore add 0.004 to your measured values around 10.

NOTE:

Guildline Autosal accuracy specified as better than +/- 0.002 in salinity over the working range (2-42)

Guildline Portasal accuracy specified as better than +/- 0.003 in salinity over the working range (2-42)

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