I know this feeling!!!
Very few of us have the equipment necessary to test or correct the equipment we test things with.....wait, what!

Best case senario is you get two independent tests to match and you can sleep a little better. I go through it all the time at work. Between me and my business partner we own 5 wood moisture metres.... we pick the 2 that are the closest that day, for the record it isn't usually the same two lol

Buy a 100 gram digital scale for like $10. Make your own fluid. Done.

you can make your own using rodi water and table salt. Randy Homes-Farley has a good article with a recipe.

i am going to make a batch and buy some of the pinpoint fluid, which from my research seems to be the most reliable fluid.

....then you have to wonder of the purity of the solution you make based on the salt....

maybe I am just a paranoid lunatic :)

Actually I made up a test solution tonight using the most rudimentary equipment (vetinary syringe and a teaspoon) and well that came out at 35ppt so I'm just going to assume my refractometer is close enough and carry on. I did however begin to wonder because of this thread so thank you thread :D

thats why you use table salt, it is pure NaCl, and the density does not change, so if you weigh it you should be good to go