Think Hydrometers Are Inaccurate Junk?

Steven Pro · 07/13/2006, 06:39 PM

You might want to reconsider,
http://www.wetwebmedia.com/ca/volume...mpressions.htm

ChemE · 07/13/2006, 06:44 PM

I had that IO one pictured on the far right for several months and one Saturday I decided to see how repeatable its measurements were. I took 5 measurements and my readings ranged from 1.019 to 1.026. I don't know how the heck you got such precision from that instrument.

LBCBJ · 07/13/2006, 06:55 PM

Yes, they are junk...that's why they're $9.99. The IO hydrometer is even junkier.

I wonder how many times he had to flick, tap, and shake those hydrometers to get those readings....

mg426 · 07/13/2006, 06:55 PM

Thats an eye opener !!

Steven Pro · 07/13/2006, 07:18 PM

Quote:

Originally posted by LBCBJ
I wonder how many times he had to flick, tap, and shake those hydrometers to get those readings....

It was an exercise in tedium to make sure there were no air bubbles on the swing arms.

Steven Pro · 07/13/2006, 07:20 PM

Quote:

Originally posted by ChemE
I had that IO one pictured on the far right for several months and one Saturday I decided to see how repeatable its measurements were. I took 5 measurements and my readings ranged from 1.019 to 1.026. I don't know how the heck you got such precision from that instrument.

The 12 that I tested were all brand new. I am now working on seeing how accurate they are after repeated use.

crumbletop · 07/13/2006, 08:38 PM

The other thing I hear frequently is that the swing arms don't do well for low SG, e.g. hyposalinity at 1.009. It would be ineresting to see how those hydrometers do at the lower SG.

Jack

ChemE · 07/13/2006, 08:40 PM

I don't know Steven. I took 30 hours of chemistry so its not like I'm unfamiliar with taking careful measurements or finessing equipment and the results I got from the IO hydrometer were very underwhelming. I find myself torn between skepticism because I know in my bones that instrument is terrible and self doubt because I really do trust you. What gives here?

ChemE · 07/13/2006, 08:44 PM

Quote:

Originally posted by LBCBJ
Yes, they are junk...that's why they're $9.99. The IO hydrometer is even junkier.

I wonder how many times he had to flick, tap, and shake those hydrometers to get those readings....

That raises another excellent point. How is one to know which flick or tap results in the correct number without knowing a priori what the true value is. Steven, post a table which shows readings after 1, 2, 3, ..., n taps/flicks/twitches/etc. That is the crux of the problem, you can get different results from the same datum just by breathing on the instrument. At least if I tap my refractometer it won't change it's reading.

PUGroyale · 07/13/2006, 08:45 PM

Largely due to the recommendations of fellow reefers on RC I felt obliged to spring for a $45 refractometer which I then used to confirm my swing arm hydrometer was... right... on.. the... money

The refractometer did give me peace of mind tho and all in all it's a much cooler gadget

Mike.B · 07/13/2006, 08:57 PM

I have an aquarium systems seatest one that is pretty much exactly what my refractometer is.

Bdimas · 07/13/2006, 09:32 PM

I just got a refractometer and i tested it against my hydrometer. They had the exact same reading. I do think that there is alot of room for error using hyrometers, ie micro bubbles or the arm being stuck.

Arik · 07/13/2006, 09:43 PM

I have an IO that I got for free, and I bought a refractometer the first time i had to treat using hyposalinity (down to 1.009). The readings were identical between the two, but I like not having to worry about microbubbles when a small change may kill an animal.

Steven Pro · 07/14/2006, 06:28 AM

Quote:

Originally posted by ChemE
That raises another excellent point. How is one to know which flick or tap results in the correct number without knowing a priori what the true value is. Steven, post a table which shows readings after 1, 2, 3, ..., n taps/flicks/twitches/etc. That is the crux of the problem, you can get different results from the same datum just by breathing on the instrument. At least if I tap my refractometer it won't change it's reading.

I did not flick or tap the hydrometers or swing arms. If I saw an air bubble, I just dumped the water and tried again. I found that if I allowed the water to enter the hydrometer very slowly, I didn't get an air bubble. But, it generally took me 2-4 attempts with each hydrometer to get a reading free from bubbles.

Roland Jacques · 07/14/2006, 06:50 AM

i have 6 hydrometer that had a lot of use. the readings seem to change OVER TIME. they are all over the place.
i calibrate them by do marking them all at 1.022. so that i can still use them. i do Aq maintenance also and i really like using them they are easy and fast. but acurate they're not.

RichConley · 07/14/2006, 07:28 AM

Quote:

Originally posted by PUGroyale
Largely due to the recommendations of fellow reefers on RC I felt obliged to spring for a $45 refractometer which I then used to confirm my swing arm hydrometer was... right... on.. the... money

The refractometer did give me peace of mind tho and all in all it's a much cooler gadget

Same.

The problem with my IO hydrometer was making sure it was 100% clean (which was tough) and keeping that little white float/weight from falling out of the arm. It would also tilt sometimes. It was inconsistent, IMO.

horkn · 07/14/2006, 07:37 AM

i have the same IO hydrometer on the far left.

i have had it nearly as long as i have had a SW tank. i had my first SW tank in 1990. At a local Wisconisn reef society meeting, we did a hydrometer / refractometer verification test. well, mine was just miorly low on the reading vs actual. not bad for all those years. and it was dirty as well, just for kicks. all the hydrometers we tested, i think between 10-15 of them, were pretty darn cloe, if not right on. we were all amazed.

Freed · 07/14/2006, 07:59 AM

I bought a refractometer, calibrated it and then checked the accuracy/precision of my hydrometer against the refractometer. I only have the refractometer now. The hydrometer was .004ppm off.

Adam · 07/14/2006, 08:25 AM

Steve,

Maybe for the next round of tests, I can make the water samples for you so that you are blinded to the values. That way, you will have to rely solely on your observation of any bubbles etc., on the arm rather than expecting a certain value.

Testing across a range is also a good idea.

I would also be interested in seeing a similar test of refractometers, especially inexpensive ones.

Adam

samsfishnchips · 07/14/2006, 08:28 AM

Quote:

Originally posted by Steven Pro
You might want to reconsider,
http://www.wetwebmedia.com/ca/volume...mpressions.htm

they have their place, but as pointed out by even the same article(only use new ones), they are ok when NEW, but the problem if any with them is not when they are new but when they get older and start to lose accuracy because of salt deposits, ect.

what I find really shocking is how people cut corners on the simple stuff

sam

07/13/2006, 06:39 PM	#1
Steven Pro Registered Member Join Date: Nov 2001 Location: Pittsburgh, PA Posts: 9,376	Think Hydrometers Are Inaccurate Junk? You might want to reconsider, http://www.wetwebmedia.com/ca/volume...mpressions.htm __________________ Steven Pro, yep that is my real name. Current Tank Info: Twelve 600 gallon tubs located in a greenhouse

07/13/2006, 06:44 PM	#2
ChemE Registered Member Join Date: Aug 2005 Location: East Nashville, TN Posts: 1,607	I had that IO one pictured on the far right for several months and one Saturday I decided to see how repeatable its measurements were. I took 5 measurements and my readings ranged from 1.019 to 1.026. I don't know how the heck you got such precision from that instrument. __________________ Holding it down on the engineering tip y'all Current Tank Info: 190G

07/13/2006, 06:55 PM	#3
LBCBJ Registered Member Join Date: May 2006 Location: Richmond, Va Posts: 1,332	Yes, they are junk...that's why they're $9.99. The IO hydrometer is even junkier. I wonder how many times he had to flick, tap, and shake those hydrometers to get those readings.... __________________ Brent

07/13/2006, 06:55 PM	#4
mg426 Registered Member Join Date: Jan 2006 Location: maryland Posts: 6,923	Thats an eye opener !! __________________ I found a way to make a small fortune running a reef tank. Start with a large fortune. Unofficial President of the SEACLONE haters club Current Tank Info: 125 mixed reef 110 lbs LR, 1x250watt XM 20K MH 2x175watt XM 20K MH on Magetics 2X96 watt actinic PC, 220 watt VHO actinic, 30 gallon refugium, closed loop system powered by Sequence Dart MSX 200 skimmer 38 gallon sump, Oceansmotions squirt

07/13/2006, 08:38 PM	#7
crumbletop Registered Member Join Date: Nov 2005 Location: Nashville, TN Posts: 4,718	The other thing I hear frequently is that the swing arms don't do well for low SG, e.g. hyposalinity at 1.009. It would be ineresting to see how those hydrometers do at the lower SG. Jack __________________ "Misers get up early in the morning; and burglars, I am informed, get up the night before." - GK Chesterton Current Tank Info: 90 gallon AGA RR. 20 gal sump. 6x54W T5. AquaController Jr.

07/13/2006, 08:40 PM	#8
ChemE Registered Member Join Date: Aug 2005 Location: East Nashville, TN Posts: 1,607	I don't know Steven. I took 30 hours of chemistry so its not like I'm unfamiliar with taking careful measurements or finessing equipment and the results I got from the IO hydrometer were very underwhelming. I find myself torn between skepticism because I know in my bones that instrument is terrible and self doubt because I really do trust you. What gives here? __________________ Holding it down on the engineering tip y'all Current Tank Info: 190G

07/13/2006, 08:45 PM	#10
PUGroyale Registered Member Join Date: Jan 2004 Posts: 2,711	Largely due to the recommendations of fellow reefers on RC I felt obliged to spring for a $45 refractometer which I then used to confirm my swing arm hydrometer was... right... on.. the... money The refractometer did give me peace of mind tho and all in all it's a much cooler gadget __________________ Dave :~)

07/13/2006, 08:57 PM	#11
Mike.B Registered Member Join Date: Jan 2004 Location: Canada Posts: 548	I have an aquarium systems seatest one that is pretty much exactly what my refractometer is.

07/13/2006, 09:32 PM	#12
Bdimas No on 15 Join Date: Oct 2004 Location: Stockton, CA Posts: 2,518	I just got a refractometer and i tested it against my hydrometer. They had the exact same reading. I do think that there is alot of room for error using hyrometers, ie micro bubbles or the arm being stuck. __________________ Bryan Current Tank Info: 90gallon mixed reef.

07/13/2006, 09:43 PM	#13
Arik Registered Member Join Date: Dec 2005 Location: Fairport NY Posts: 593	I have an IO that I got for free, and I bought a refractometer the first time i had to treat using hyposalinity (down to 1.009). The readings were identical between the two, but I like not having to worry about microbubbles when a small change may kill an animal.

07/14/2006, 06:50 AM	#15
Roland Jacques Premium Member Join Date: Mar 2003 Location: Atlanta GA Posts: 2,848	i have 6 hydrometer that had a lot of use. the readings seem to change OVER TIME. they are all over the place. i calibrate them by do marking them all at 1.022. so that i can still use them. i do Aq maintenance also and i really like using them they are easy and fast. but acurate they're not. __________________ Roland

07/14/2006, 07:37 AM	#17
horkn Registered Member Join Date: May 2004 Location: milwaukee wisconsin Posts: 4,125	i have the same IO hydrometer on the far left. i have had it nearly as long as i have had a SW tank. i had my first SW tank in 1990. At a local Wisconisn reef society meeting, we did a hydrometer / refractometer verification test. well, mine was just miorly low on the reading vs actual. not bad for all those years. and it was dirty as well, just for kicks. all the hydrometers we tested, i think between 10-15 of them, were pretty darn cloe, if not right on. we were all amazed. __________________ people write stupid things in this space Current Tank Info: 200g DIY wood reef, 2x 250w SE 10k MH 2x80 t5ho, 75g sump, Geo Ca RX, ASD 6" recirc skimmer

07/14/2006, 07:59 AM	#18
Freed It's what it's Join Date: Mar 2003 Location: 41° 2' 45" N 85° 8' 43" W Posts: 7,579	I bought a refractometer, calibrated it and then checked the accuracy/precision of my hydrometer against the refractometer. I only have the refractometer now. The hydrometer was .004ppm off. __________________ Freed Current Tank Info: 180gal(1120 watts of MH/VHO light), 60gal "sump", Deltec 601 calcium reactor, Euro Reef CS8-3+ skimmer, 20 gallon QT

07/14/2006, 08:25 AM	#19
Adam Registered Member Join Date: Jan 2001 Location: Pittsburgh, PA Posts: 1,190	Steve, Maybe for the next round of tests, I can make the water samples for you so that you are blinded to the values. That way, you will have to rely solely on your observation of any bubbles etc., on the arm rather than expecting a certain value. Testing across a range is also a good idea. I would also be interested in seeing a similar test of refractometers, especially inexpensive ones. Adam __________________ Everyone has the right to be stupid, but some people abuse the privilege. Current Tank Info: 120 mixed reef