Refractometer calibration never consistent

[dr_ fish]

I have a refractometer that I have had for a few years. I recently bought 35ppt calibration fluid for it and followed the procedures to calibrate it at 35ppt.

I go to test my tank and it says I am at 1.022 S.G. I then clean it off, put the 35ppt calibration fluid back on and it now test at about 38ppt. I went back and forth several times and get numbers that vary.

What gives? I constantly get inconsistent numbers.

Need a new refractometer?

 

[ripped tide]

Temp plays a role, as well as residual salt from previous test

Edit: The refractoneter measure the speed that light passes through the water. Different temps will slow down or speed up the light as it is measured.

 

[dr_ fish]

Ripped Tide;761135 wrote: Temp plays a role, as well as residual salt from previous test

Edit: The refractoneter measure the speed that light passes through the water. Different temps will slow down or speed up the light as it is measured.

It is a temperature correcting model, and I wait 45 seconds for the temp to equalize between the prizm and water.

I also, clean it off before AND after each use. There is no residual salt.

 

[ripped tide]

Hmmm, seems like you have all the basics covered, especially if it is temp correcting.


Have you recently dropped it? I've noticed that some will loose calibration If you shake it around to hard or drop it.

I was having issues with a Second hand refractometer that I bought from a member. It was probably dropped or damaged at some point, because keeping calibration seemed impossible.

 

[ripped tide]

For what it is worth, I could never get the used refracto to work. I ended up using a dremel and disassembling it to see how it works.

 

[dr_ fish]

Guess ill buy a new one. Maybe it got dropped or damaged somehow. I have had it for years.

 

[stickx911]

made me think to get mine checked. I've had the same one for years, and never really thought it would need to be calibrated much. Probably about time I do that. haha

 

[ripped tide]

I've gotten to where I check mine before every use.

 

[grouper therapy]

Use a hydrometer and don't worry about. If properly cleaned and used I have never had one be off.

 

[ralph atl]

Get this:

http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=12132">http://www.drsfostersmith.com/product/prod_display.cfm?pcatid=12132</a>

Never out of calibration.....those cheapies always have to be calibrated, pia.

 

[fishlips]

grouper therapy;761223 wrote: Use a hydrometer and don't worry about. If properly cleaned and used I have never had one be off.

My swing arm is 5 yrs old, and dead on with my refractomter.

 

[spankdog]

I was just thinking the same thing last night after measuring my water and finding it way off. Got the calibration fluid out and discovered that the refractometer was way off instead. Re-calibrated it and then checked water and it was fine. I have the $50 one from marinedepot

 

[mustangcaleb]

i need to test mine also, ive noticed the last few weeks that according to my refracto, my salinity isnt going up with evap. i check it before and after every top off

 

[stickx911]

any reason using distilled @ 0 is a bad idea?

 

[acroholic]

Here's the one I use...one of the best equipment buys I have done: Milwaukee MA887 Digital Refractometer. No more visual calibrations. Dead on accurate, and easy to use. You can buy this for the same price as the ocular one Ralph posted.

Here's my product review for it from 2010:

http://www.atlantareefclub.org/forums/showthread.php?t=43427&highlight=digital+seawater+refractometer">http://www.atlantareefclub.org/forums/showthread.php?t=43427&highlight=digital+seawater+refractometer</a>

Link for typical purchase:

[IMG]http://www.marinedepot.com/ps_viewitem.aspx?idproduct=4M00600&child=4M00600&utm_source=mdcsegooglebase2&utm_medium=cse&utm_campaign=mdcsegooglebase2&utm_content=PST2-4M00600">http://www.marinedepot.com/ps_viewitem.aspx?idproduct=4M00600&child=4M00600&utm_source=mdcsegooglebase2&utm_medium=cse&utm_campaign=mdcsegooglebase2&utm_content=PST2-4M00600</a>

 

[stacy22]

It's best to calibrate to a known value that's close to what you will be measuring. Seawater is closer to the 35ppt value than 0ppt.

Ricky, glad to see you back!

 

[dawgface]

Acroholic;761364 wrote: Here's the one I use...one of the best equipment buys I have done: Milwaukee MA887 Digital Refractometer. No more visual calibrations. Dead on accurate, and easy to use. You can buy this for the same price as the ocular one Ralph posted.

Here's my product review for it from 2010:

http://www.atlantareefclub.org/forums/showthread.php?t=43427&highlight=digital+seawater+refractometer">http://www.atlantareefclub.org/forums/showthread.php?t=43427&highlight=digital+seawater+refractometer</a>

Link for typical purchase:

[IMG]http://www.marinedepot.com/ps_viewitem.aspx?idproduct=4M00600&child=4M00600&utm_source=mdcsegooglebase2&utm_medium=cse&utm_campaign=mdcsegooglebase2&utm_content=PST2-4M00600">http://www.marinedepot.com/ps_viewitem.aspx?idproduct=4M00600&child=4M00600&utm_source=mdcsegooglebase2&utm_medium=cse&utm_campaign=mdcsegooglebase2&utm_content=PST2-4M00600</a>[/QUOTE]


+1 One of the best investments I've made so far!

 

[ralph atl]

Acroholic;761364 wrote: Here's the one I use...one of the best equipment buys I have done: Milwaukee MA887 Digital Refractometer. No more visual calibrations. Dead on accurate, and easy to use. You can buy this for the same price as the ocular one Ralph posted.

Here's my product review for it from 2010:

http://www.atlantareefclub.org/forums/showthread.php?t=43427&highlight=digital+seawater+refractometer">http://www.atlantareefclub.org/forums/showthread.php?t=43427&highlight=digital+seawater+refractometer</a>

Link for typical purchase:

[IMG]http://www.marinedepot.com/ps_viewitem.aspx?idproduct=4M00600&child=4M00600&utm_source=mdcsegooglebase2&utm_medium=cse&utm_campaign=mdcsegooglebase2&utm_content=PST2-4M00600">http://www.marinedepot.com/ps_viewitem.aspx?idproduct=4M00600&child=4M00600&utm_source=mdcsegooglebase2&utm_medium=cse&utm_campaign=mdcsegooglebase2&utm_content=PST2-4M00600</a>[/QUOTE]


That's what I would get! However, mine works so well...but if it breaks.....at that price, why not?

 

[acroholic]

mysterybox;761455 wrote: That's what I would get! However, mine works so well...but if it breaks.....at that price, why not?

Yea, I bought mine when my cheapo ocular one couldn't hold a calibration. Yours is a nice one.

 

[jennm]

I've had the same el-cheapo one I use at the shop for about 10 or 11 years now. Handle it with care, calibrate it regularly but it holds calibration.

I see a lot of refractometers much newer than mine, that rust out because they're put away moist in a sealed box - mine sits in an open box on the counter - it's cleaned off after each use but we don't close up the box (we lost the lid somewhere along the way). It's still going strong.

I do see a fair amount of folks who bring in theirs for calibration that lose calibration and there doesn't seem to be a common thread between brands.

My service tech seems to eat refractometers -she's gone through probably a dozen of them in the last 8 years - but hers is riding around in her truck with her, being brought into every home and office, probably gets bumped around, dropped and otherwise abused - I just expect she'll need a new one every 6 months or so :lol:

Jenn