hydrometer accuracy?

[JeffGil]

OK, quick question hopefully.

We're currently using cheapo plastic Deep Six and Instant Ocean hydrometers and they generally give us different salinity readings. I've been sticking with the Deep Six one as that's what I started with and everything in the tank seems happy, but the fact that the second hydrometer gives different readings makes me nervous.

Are the TM hydrometers more accurate? I'm contemplating getting one of the floating ones that gives salinity and temp in one device like the top one at: http://www.gandwinstruments.com/products.htm

Are those better, more accurate, and dependable than the plastic ones or should I just go buy a refractometer and get it over with?

 

[Boomer]

It is not that the TM or StayRite are more accurate it is that they are more reliable. The issue with many swing arms is that people do not keep up the maintenance required or get frustrated with the bubbles clinging to the arm. You do not need and of those hydrometers on that web, as then you will be struck using tables or on-line calculators to see what your "true" sg is, as they are cal to 15 C and not 25 C such as the TM. The TM is a very good hydrometer.

As far as the Deep Six goes, it is about the most inaccurate swing arm there is from tests with the IO being the best.

That StayRite is a nice unit but I do not see anything on the website about the scales they are using. So, I talked to the onwner of the company today You can not buy a StayRite unless you buy 12 of them. They only make them now in a special request order. One of their std hydros is ~ $15 and cal to 60 F(15C) or if you have lots of money they also have NIST-T for around $150.00 A true NIST is ~ $1500.00 :lol:


Almost any hydro's just frustrates one for one reason or another. Just get a good refract with ATC. Easy, quick, no tables to use, no swinging, not bobbing around and do not break as easy as hydro's.

For use, this is the best refract sold in the hobby.

http://thefilterguys.biz/refractometers.htm

 

[JeffGil]

"As far as the Deep Six goes, it is about the most inaccurate swing arm there is"

ARGHGHGH %^&*@*&#^!!! figures lol

Thanks for the information Boomer. I found this portable refractor on Doc Fosters & Smith for 1/2 the price of the other one, is the other one worth the extra $$$?

Figures, I just ordered the REEF FANATIC TOP-OFF LEVEL CONTROLLER from that site yesterday (having second thoughts about the RO/DI going straight to the sump with one float valve so going with an auto top-off and only using the filter to manually fill up the top-off when needed).

 

[Boomer]

Well I'm not you and I would get the one from the filterguys Do you have to have it, no, the other one is Ok.

 

[Jan]

is the TM hydrometer mentioned above made by Tropic Marin? Who sells these?

I think it's a good idea to have an accurate device that's not a refractometer (since they can drift), and compare the two every so often. I bought a floating glass hydrometer today for that purpose.

Now I can tell you that my cheapo plastic swing arm hydrometer, the new glass hydrometer, and my refractometer all match exactly. (Not so the refractometer from the LFS I went to today, who measured their systems sg as 1.026 with their refractometer while mine measured it at 1.021...)

 

[Scooterman]

http://www.aquabuys.com/miva/mercha...ms_hydrometer&Category_Code=r2&Store_Code=aqb

I'd bring some of your Pinpoint Test solution to the LFS & ask to check your water again, then ask to test it with the Pinpoint solution, I bet they are off.

 

[Jan]

I did bring my pinpoint solution and asked them to test their refractometer with it, and their refractometer read it at 1.030. But then the guy said, "The directions say to calibrate wtih freshwater so that's what I do."

Maybe he just wanted to wait for me to walk out before he calibrated it.

 

[Scooterman]

http://www.strictlypetsupplies.com/_619106510025-TROPIC-MARIN-PRECISION-HYDROMETER

Another store to get it, apparently it isn't as common as it once was but I don't think I'll ever trade off mine

 

[Boomer]

Jan, then that is the LFS to stay away from

 

[Jan]

yeah, I only stop in their for certain things because they're on my way home from work.

 

[Vicki]

I think it's a good idea to have an accurate device that's not a refractometer (since they can drift), and compare the two every so often. I bought a floating glass hydrometer today for that purpose.

Now I can tell you that my cheapo plastic swing arm hydrometer, the new glass hydrometer, and my refractometer all match exactly. (Not so the refractometer from the LFS I went to today, who measured their systems sg as 1.026 with their refractometer while mine measured it at 1.021...)

I wasn't aware that the PinPoint solution could be used on a refractometer until I read this. I've got to get some of that! I thought it was just for the Salinity Monitor. One of those 'learned something new' for today!

Once you've calibrated the refractometer with the PinPoint solution, does RO/DI water show zero?

Vicki

 

[Jan]

Once you've calibrated the refractometer with the PinPoint solution, does RO/DI water show zero?

I think it depends on the specific refractometer and whether it has any slope irregularity. On mine, RO/DI water no longer shows at 0, that reading is now well below the 0 point. So mine is now calibrated to read correctly at 35 ppt but won't read correctly at the 0 point anymore. (I had to reread the sticky article on refractometers in order to not be worried about that fact anymore...)

 

[Vicki]

I think it depends on the specific refractometer and whether it has any slope irregularity. On mine, RO/DI water no longer shows at 0, that reading is now well below the 0 point. So mine is now calibrated to read correctly at 35 ppt but won't read correctly at the 0 point anymore. (I had to reread the sticky article on refractometers in order to not be worried about that fact anymore...)

Thanks Jan... Guess this is something we all should check.
I did go and read the article, plus found the other current thread.

Vicki

 

[Jan]

I agree that this is very important...I know a guy that had a complete SPS tank wipe-out last summer caused by two things happening together: his refractometer was faulty (even after calibrating with pinpoint it was still 10 points off), and his reliance on Salifert alk tests which have had some bad batches recently and read well off actual Alk levels.

 

[Scooterman]

That Jan Is where you need to have the TM floater, it is like trying to read an accurate temperature with a probe & digital thermometer, to me the old glass mercury Is hard to beat. JMO though!

 

[Jan]

I'm with you on that, Scooty. I just bought a TM hydrometer...thanks for posting that link!