Problem with digital refractometer

[Wilsontank]

So I been recently measuring my salinity with the Milwaukee refractometer and it hasn't been accurate. First I get 1.022 and out of curiosity I pressed read again with the same water sample and it goes up to 1.023. Then after a few other tries I get 1.024. I'm so confused !!! Has anybody has a similar problem with this device ? I read it's really reliable. I'm probably doing with wrong. Please help thanks '

 

[disc1]

The longer that little drop of water sits there, the more of it evaporates. The more it evaporates the higher the SG goes. How long was it between the different readings?

 

[Wilsontank]

Seconds. I kept taking out different samples though. It really doesn't make sense. I don't really understand what calibrating does or what it is but I also did it before use.

 

[Marchillo]

I posted something similar recently. With the same exact sample I only vary between .01 if I keep reading. Meaning I'll get 1.023 then 1.024. I haven't experienced 1.023 to 1.025 with the same sample. Does that always happen? When I pull my sample I always flush out the pipette 2-3 times. Try not to touch it on anything with salt creep. Since my first couple days I have gotten more consistent readings. I always calibrate it. If you go 1.023 to 1.024 to 1.025 try getting another sample and see if it continues.

But yes I understand your pain. It doesn't give you confidence with the varying results.

 

[Marchillo]

Yes calibrating helps. When you put the solution on sometimes it will read 1.001. The calibrating will zero that out.

 

[theatrus]

Also, a drift could be the temperature compensation in action. It doesn't compensate to the water, rather the prism is compensated and the water gets to that temperature.

 

[remix8315544]

I have the same one. It's been very accurate

 

[laga77]

The Milwaukee that I have has operated very well. Just a guess here, Your water sample is on the edge of reading between 1.022 and 1.023. Now, throw in the margin of error of the device, .001 IIRC, and you get a reading of 1.024.