Digital salinity pens

[Johnny M]

1. Hope this is in right forum. I just received the new Poisiden salinity pen+, along with an icecap pen I got about 3months ago and also checked with a Milwaukee digital refractometer. So I tried all 3 on a batch of SW made 1 week ago : 2- 32g Brute trash cans : *Note - Milwk. & poisiden calibrated with 30ppt salinity reference solution. Milwk. = 29ppt ; Poisiden = 30ppt. *Using HW Marine reef salt and always add same amount to get 1.025. Measured in S.G.

Milw. refractmter : Brute #1 = 1.026 Brute #2 = 1.025

icecap pen : Brute #1 = 1.023 Brute #2 1.023

poisiden pen+ : Brute #1 = 1.023 Brute #2 = 1.023


Now Milwkee meter & icecap pen say +/- .0002 ; poisiden states +/- .001
QUESTION : Which tester should I believe? I always thought the Milw. refratmtr was accurate, whereas I've read the Icecap salinity pen can be off by more than +/- .002.

 

[wesman42]

Have you checked any of these results with a calibrated refractometer? All of the devices you mentioned are electronic, and thus you can't really use one or the other for checking accuracy.

Redundancy is key, but if I had to guess, Is say the Milwaukee digital is the most accurate. Simply because I've seen then being used....I have not see pens of any kind.

 

[Forsaken77]

Just a quick fyi... With the Milwaukee, make sure to rinse the glass with rodi after every use. I was just drying it off in the beginning because it left a film and it threw the readings way off, not to mention the Milwaukee reference fluid was off as well.

Also check your rodi water, that it reads 1.000.

I have read about a few of the Icecap pens not reading correct, but have no first hand use.

 

[Johnny M]

I clean the milwaukee refractometer always with rodi water that reads 1.000 b4 & after each use. A couple of months ago online with reef builders they tested the new poisiden pen with Hanna digital refractometer using 35ppt salinity reference solution and both instruments dis played 37ppt. The final opinion in the article was that the poison pen+ was just as accurate as the Hanna meter.
I don't use a calibrated refractometer bc eyesight is not what it use to be & have also read many opinions that calibrating a manual refractometer can be difficult - air bubbles , lens not cleaned properly , using just the right amount of light, etc..., that's why more & more SW hobbyists are using digital ones.