Could you provide a link showing the tester that you got? I would like to check something.
About what I got, I am in the USA, but if you want to focus just in salinity, do not go fancy. Mine supposed measure pH, but have not worked in a while, so you only need one good salinity measure, because the most common salinity measurement are equivalent.
For example, for average Ocean Water:
- 3.5% ( Salinity Percentage)
- 35 ppt ( Parts Per Thousand)
- 1.026 sg (Relative Specific Gravity).
For what I have seen, often Specific Gravity provides the least numerical precision of calculations.
% and ppt look to be better for calculations.
The one that I got, with "backlight" was $57.99 in USA Dollars.
https://www.amazon.com/gp/product/B0885YXFJ6
So this time, I did search "digital salinity ppt".
Ouch! I tried different words to search, but as soon you put "digital" and "salinity" together, although it gave me what I wanted, the price would jump up.
Below is the link of the cheapest I found that I would trust to buy today.
The price presented is $35.90 in USA Dollars.
There were others that were half the price, but always those would not have more than 5 reviews, and always would be 5 stars. So I do not trust them.
If you cannot find a reasonable digital version, then you want to go with a Refractometer, that often are more reasonable priced.
The only problem with mine, was that after a few months I had problems focusing the eye piece to see properly the lecture. :(
That said, whichever you decide to get, try to find different sources of reviews.
The higher the number of reviews, more trust I put in the net raking that the product gets.