Just bought a Red Sea refractometer. Seems like the worst investment ever. It will not hold calibration between tests most times, and I don't mean the following day. I mean it looses calibration between the time I calibrate it to when I test the water and then check the calibration fluid. I calibrate, test tank water, and then test calibration fluid and the refractomter is off by a few PPT in one direction or another, different each time. I am not sure if this is just a faulty unit but that seems outrageous. I cannot trust any result it gives me.
I have even calibrated it to the standard solution and then checked it on RO/DI water and then when retesting the calibration fluid I received different results. Further I have double checked this with a cheap BRS or amazon unit that I borrowed and confirmed the poor results. When calibrated using RO/DI fluid the unit tests out at 0 ppt. However, when I then go and look at the calibration fluid it reads between 30 and 33 ppt. Yes I dry off the refractometer lens between tests. I am at a loss for what to do other than throw it away.
The ambient temperature is high 60s and the same light source is used for all tests. While I realize temperature plays a role in accuracy it should not, when kept constant, impact the precision of the units.
I used to have a really cheap one that I used for years until I knocked it off a table onto the concrete floor. I'm hoping it is my testing method or that the particular unit is defective. Does anyone else have this problem with Red Sea's refractometer? Any suggestions?
I have even calibrated it to the standard solution and then checked it on RO/DI water and then when retesting the calibration fluid I received different results. Further I have double checked this with a cheap BRS or amazon unit that I borrowed and confirmed the poor results. When calibrated using RO/DI fluid the unit tests out at 0 ppt. However, when I then go and look at the calibration fluid it reads between 30 and 33 ppt. Yes I dry off the refractometer lens between tests. I am at a loss for what to do other than throw it away.
The ambient temperature is high 60s and the same light source is used for all tests. While I realize temperature plays a role in accuracy it should not, when kept constant, impact the precision of the units.
I used to have a really cheap one that I used for years until I knocked it off a table onto the concrete floor. I'm hoping it is my testing method or that the particular unit is defective. Does anyone else have this problem with Red Sea's refractometer? Any suggestions?
