Im using a PLC , solenoids, and a pressure transmitter in inches of water column (4-20 ma)....premixed salt water tank, RO tank for top off, 3 RTD inputs for temperatures (of all 3 tanks), pH probe input, etc..... I always use the same salt and know the amount of salt needed to make 25 litres of salt water, but I'm pretty sure I can be there for the actually test of the SG.
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