Which salinity reading would you trust more

[Anonymous]

The reading from a calibrated refractometer or the reading from a calibrated electronic pinpoint salinity monitor?

 

[Anonymous]

Sounds like a trick question to me. I think either would be equally adaquate if properly calibrated.

 

[tinyreef]

refractometer.

i don't all those electronical-dohickey stuff. robot overlords and all that.

 

[Fastmarc]

I have seen quite a few articles that states conductivity to be the most presise way to measure salinty and the Pinpoints have a good reputation. I have been using one for some time and finds it works well.
Here is an article done by Randy Holmes-Farley on Conductivity.
"Using Conductivity To Measure Salinity"
http://www.aquariumfish.com/aquariumfis ... x?aid=1804

 

[LA-Lawman]

i think it would be a matter of how much do you want to spend to determine salinity??? :?

I would say if you can get a refractometer then do it. if you can afford a ferrari then buy the conductivity one....

 

[Anonymous]

Sorry I was totally unclear!

I happen to have both, and after calibrating both, they don't agree. The refractometer reads 35 (1.026) while the pinpoint reads 29 (1.0214).
That seems to be a robust difference in readings.

 

[LA-Lawman]

well if you would get that octopod off your head, you could probably think straight!!

i dunno... u might send a message to delbeek a local aquarium... maybe Sanjay could help... u might need a scientist for this one.

 

[tinyreef]

Sorry I was totally unclear!

I happen to have both, and after calibrating both, they don't agree. The refractometer reads 35 (1.026) while the pinpoint reads 29 (1.0214).
That seems to be a robust difference in readings.

actually, that's what i figured you meant.

my thinking (joking aside) was that the pinpoint should be more accurate but it also probably has more things to go wrong with it (imo).

the refractometer could still be off (e.g. angle of the plate could be slightly off-kilter) but i'm figuring you'd see something like that or feel it. the sight glass could be off in light transmission quality, etc. but i would think (hope) the mfg company has some qc standards that covers something as basic as that. famous last words.

both being calibrated really puzzles the issue though. still i'd figure the refractometer being more trustworthy in such a conflict situation.

otoh, if it were 1.026-refract versus 1.025-pinpoint, i'd probably side with the pinpoint. i hope that doesn't make me a hypocrite.

 

[Anonymous]

Dont they measure two different things?

I believe salinity meters only look at NaCl

where a refractmeter uses a refractive index

did you test the same solution with both? I would use straight salt to test both, using the same solution sample

I would trust the refractometer over the probe

 

[Anonymous]

Did you calibrate with 35ppt water or 0ppt or something in the middle?

 

[Anonymous]

I calibrated the refractometer with distilled and the monitor with a 53 solution.

 

[Anonymous]

Isnt there a way to use salt to calibrate them both using the same solution?


I read a little bit about it, then I got sidetracked on pinpoints calcium monitor

 

[Anonymous]

I'd trust the monitor then.

Randy Holmes-Farley did an article a while back that showed Refractometers only being accurate consistently when calibrated with a 35ppt solution. I think it was the same article where he wrote about the recipe for a homemade calibration solution using a pop bottle and table salt.

 

[Anonymous]

Yeah. And the monitor reads 53 after being put into the tank and back into the test solution.

I'll mix up my own solution when I get time.

 

[Anonymous]

Just use the 53 solution on the refractometer, it should read 1.0264 sg

refractive index of 1.33940

 

[Anonymous]

The 53 solution does not read 1.0264 on the refractometer, it reads 1.020.

 

[Anonymous]

BTW, RHF says it is not necessarily the case that the 53 solution will read 1.026 on a refractrometer.

 

[GSchiemer]

I'd probably trust the refractometer simply because there's less probability of a malfunction.

FWIW, Salifert makes a 35ppt reference solution for use with refractometers. I used it to calibrate my refractometer and then measured DI water. It read a perfect "zero," so I believe that DI water can be use to accurately calibrate a refractometer.

Greg

 

[cygnus]

go with the refractometer, no chance of changes in readings due to power fluxes, weak battery, and i KNOW for a fact my pinpoint PH meter would fluxuate up and down when my chiller would cycle on. True a refractometer measures more than just salt but since 99% of the your tank water will be NaCL the difference is not statisticaly significant. THe pinpoint monitor can change on you from so many outside factors that you cant measure or are out of your control. As long as you keep your refractometer clean and zeroed out with distilled or RO/DI water. The only reason i see that it could go out of wack is if the speed of light suddenly changed.

 

[Anonymous]

If you want to really know what the answer is, do what I do....


Use a good old swing arm hydrometer.

I will let you borrow mine if you want, been using it for years, nary a problem yet. Although sometimes it gets really full of salt and gunk and I have to clean it out before using it....