Hi Namrata,

Pilson (1998, An Introduction to the Chemistry of the Sea, Prentice Hall) describes the precision of three common methods for measuring salinity in water as:

1. hand-held refractometer - 1 part in 70

2. laboratory titration - 1 part in 350

3. modern salinometer - 1 part in 40,000

some relevant links are attached below. Hope you find them helpful.

http://agriculture.vic.gov.au/agriculture/farm-management/soil-and-water/salinity/measuring-the-salinity-of-water

http://www.osil.co.uk/AboutOSIL/Resources/NewsArticles/tabid/114/articleType/ArticleView/articleId/267/Measuring-Ocean-Salinity-in-the-Laboratory.aspx

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwjMuqyyoKnUAhWMQY8KHb1DAgYQtwIIQDAE&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DwzhwTnkKWzs&usg=AFQjCNGsMBHq1mRj2onQjHzkqgwbYvJ2JA&sig2=aYfZ3P0feA8euXTDCMpnUA

https://www.google.co.in/url?sa=t&rct=j&q=&esrc=s&source=web&cd=6&cad=rja&uact=8&ved=0ahUKEwjMuqyyoKnUAhWMQY8KHb1DAgYQFghGMAU&url=https%3A%2F%2Farchive.org%2Fstream%2Fmeasurementofsal00usco%2Fmeasurementofsal00usco_djvu.txt&usg=AFQjCNHEN6l55rpxiNX3-v718SoWVpjy2g&sig2=3Jh044zRyH5pAQicg5h7uw

Here are a couple of web references:

https://www.windows2universe.org/?page=/earth/Water/dissolved_salts.html

https://www.epa.gov/sites/production/files/2015-09/documents/2009_03_13_estuaries_monitor_chap14.pdf

The Oceans Their Physics, Chemistry, and General Biology (section on salinity)

http://publishing.cdlib.org/ucpressebooks/view?docId=kt167nb66r&chunk.id=d3_1_ch03&toc.id=ch03&brand=eschol

CTD sensor

http://www.oceannetworks.ca/sites/default/files/pdf/learning/community_observatories/instrument_overivew_CTD_19Aug2014.pdf

http://www.misco.com/Downloads/MISCO-TB-SEAWATER.pdf

Standard Methods for the Examination of Water and Wastewater has a small section on salinity. The entire document is available in many libraries,otherwise it must be purchased from https://www.standardmethods.org/

I believe the latest edition is 22nd Edition, 2012, ISBN: 9780875530130, 1496 pages

Author: E.W. Rice, R.B. Baird, A.D. Eaton, L.S. Clesceri, editors

Publisher: American Public Health Association, American Water Works Association, Water Environment Federation

The international thermodynamic equation of seawater – 2010: Calculation and use of thermodynamic properties

http://unesdoc.unesco.org/images/0018/001881/188170e.pdf

Salinity - it's definition and calculation

http://www.dfo-mpo.gc.ca/Library/54855.pdf

Hope this helps!

It's always a contradiction between a "most suitable" and a "most accurate" methods. There are many suitable instruments to measure salinity, but only a few of them are most accurate (and most expensive).

The most suitable method to measure marine salinity is using submersible CTD probes. There are many companies, who manufacture reliable and accurate CTD probes. In my opinion, the most accurate CTD probes are made by:  

https://www.seabird.com

https://www.rbr-global.com 

The most accurate method to measure seawater salinity is a salinometry - the laboratory measurements of salinity samples. The most accurate salinometer is Autosal 8400B, with accuracy (in a practical salinity equivalent)  +/-0.002, manufactured by  

https://www.guildline.com

For the salinometry history, methods, instruments, calculators, references, literature etc,   I can recommend my informational website: https://www.salinometry.com  

Thank you so much, all of you, your suggestions are really very helpful to me. :-)

is there any equation available for the conversion of EC to salinity ? I am working on wetlands

For your objective, you can even use Refractometer for quick measurement of salinity.