If you look at the mechanical salt meter, they are mostly used with higher concentrations of salt, such as used with salt water fish tanks (above 20,000 ppm). A simple salt solution standard that will give about 3000 ppm is to mix two packets of Wendy's salt to 16 oz (a 1/2 liter bottle of water with these two packets will come out to about 2800 - 2900 ppm of salt).
I have used the MyronL meter calibrated for NaCl and am currently using the LaMotte Pocket Tracer. Both are very accurate, battery operated meters but are mostly based in conductivity. The good thing is that you can make assumptions between conductivity (TDS) and salinity.