When brining meats using a home made mix you need to be sure that you have the correct % of salts in the fluid. The qty of salt in the water will tell you how long to soak your meats in the brine.
A Salinometer is a specially built glass tube with a weight in the end, this tube is sealed which allows it to float in the water. The tube will sit at a certain level in the water and will show you on the built in indicator the level of salt you have achieved, which helps you determine the time needed to brine your meats.
Simply fill a tall jug with your brine mix and place the salinometer into the water and check the reading.
Brine measures are commonly used as part of the bacon making process.