Refracto Meter

[Aquatic Dreams]

HMMMM ... I recently bought some solution and used it to calibrate my Vertex. It was off by a bit but not much. Maybe I should double check with my RO water.

 

[TORX]

IMHO, calibrating to 0 isnt going to help. Great, that means you know if your water is 0...what about if you want 1.026? Just because 0 is right, does not mean that 35 is correct ppt. Maybe it would help to get calibration fluid that is the range you are looking for. DO that with 0 and you will know that your refractometer is reporting the same across the board.

 

[Aquatic Dreams]

IMHO, calibrating to 0 isnt going to help. Great, that means you know if your water is 0...what about if you want 1.026? Just because 0 is right, does not mean that 35 is correct ppt. Maybe it would help to get calibration fluid that is the range you are looking for. DO that with 0 and you will know that your refractometer is reporting the same across the board.

That's what I was thinking. Calibrate with the solution and then check with the RO water as mentioned earlier. Does it matter that my RO water is 4 TDS? It should still be zero salinity correct?

 

[TORX]

That's what I was thinking. Calibrate with the solution and then check with the RO water as mentioned earlier. Does it matter that my RO water is 4 TDS? It should still be zero salinity correct?

Exactly. SO long as there is no salt in that 4TDS. Which I would assume not. 0TDS would be ideal, but only next to 35PPT solution as well.

 

[Aquatic Dreams]

Exactly. SO long as there is no salt in that 4TDS. Which I would assume not. 0TDS would be ideal, but only next to 35PPT solution as well.

OK Cool. I'm not using DI in my RO system. But I was previously using hardware store water which I THOUGHT was RO water. Only to find that it was sitting at around 110 TDS. I was getting 6 TDS from my RO system a few weeks ago but am now getting 4 TDS. I'd been using the hardware store water since last August up until about a month or so ago. So in reality I'm happy with anything under 10 TDS.

I just wanted to make sure that it wouldn't skew the salinity reading which I didn't think it would. I originally calibrated using the hardware store water which may explain the slight difference in measurement when I calibrated with the solution.

 

[zoomster]

IMHO, calibrating to 0 isnt going to help. Great, that means you know if your water is 0...what about if you want 1.026? Just because 0 is right, does not mean that 35 is correct ppt. Maybe it would help to get calibration fluid that is the range you are looking for. DO that with 0 and you will know that your refractometer is reporting the same across the board.

Thats pretty much what I mean.
I myself would never use only DI to calibrate my refractometer.
I have professionally made calibration fluid so I am quite confident in its accuracy. So what I do is calibrate with the fluid, then check it against 0 ppm DI.
Then I do it again and if the results are identical and where they should be, I am satisfied.
Since unknown calibration fluids and even DI for that matter are susceptible to "inaccurate" and "False" readings ( and really, how would we truly know? ) we can only verify to a certain extent. At some point We have to trust and have faith that our methods are acceptable and as accurate as possible.

 

[Pistol]

If calibrating it to 0 and checking it with fluid and calibrating with fluid and checking for 0 are the same then why waste the money on fluid.
Also I have a Milwaukee digital refractometer, can't be calibrated, must be zeroed with RODI.
The drift in these meters is negligible, your more likely to have a problem with bad solution than bad RODI.