Here a link to the user guide for the Extech RF10 and RF16 (ATC).

http://www.extech.com/instrument/products/alpha/manuals/RF10_15_UM.pdf

I believe a Brix refractometer can be as valuable as a pH and EC meter if used properly.

Are you saying the instrument you referred to could also be used as a pH & EC meter? I did not see the specifications on the users guide. Or - do you mean by measuring the brix it would help determine if you had run your system at the right pH & EC?
I have always thought a brix would be a good idea to use in a study  to measure the effectiveness of hydro versus soil. It would be a concrete way of looking at taste. There are so many studies with parameters looking at soil based crops using a brix that it would make the work easier for hydro growers. Tomatoes, squash melons, apples, grapes, strawberries, apples - even lettuce - are just a few of the crops.
Do you have a specific crop in mind?

Hi Baci. Sorry if I was not clear. I meant the BR can be as valuable (read useful) as a pH and/or EC meter. You are correct in that the BR can determine quality of the fruit you are growing by measuring its sucrose level.

Obviously one would not use a BR until the fruit is ready for harvesting. Also the need for record keeping is important. One can test various nutrient formulas and measure quantitatively the results.

Specifically I had cherry tomatoes in mind. BTW I've seen BRs with ATC on eBay for about $32 + shipping.

Thanks, Hank  now I get it. The 30 dollar prices are reasonable. It is amazing how many things this meter is used for  even wine & soda.
The nice thing about your idea is you could do it with a limited amount of room & within a short period of time. You could probably get samples from companies, but they might not like it if their product does not perform well.
My idea was to use it to use the Brix to test hydro melons, but I still need to get my melon method down yet.

Wow I would love to grow melons hydroponically. That's the holy grail of hydro gardening in my opinion.

The melon foliage grows pretty easily in Perlite, but blooming & fruiting is another matter. The last time I tried I used the soil based nutrient, which just does not work. The problem is Perlite is not a good media for high sun areas, & melons bloom during times of high heat. They grow melons commercially in CA in an area that used to be desert land, so maybe they can tolerate sand. My next attempt will probably be to try hydro nutrient & sand. Whitefly is also a problem.

By the way, that cherry tomato looks like a good pick for hydro. I was reading the other day they were resistant to blossom end rot. Once again, you are ahead of us.

Wine and soda? Try blood and urine! Refractometers can be used to test many things, but they can/will give false results (* peroxide, vinegar, oil, gas, and many other
liquids). Nonetheless, great tool.

The downside is that hydroponic growers get blasted by their soil counterparts over low brix readings. Soil wins hands down (*probably) due to the complex soil food web that is constantly at work predigesting nutes and minerals for your plants.