Reflactor calibartion Verfication

L

lastduke

New member
Does anyone around Orinda area have a calibrated reflactor? I just followed Randy's article to calibrate my reflector, but I really doubt I might do something wrong when I made the stardard. If you have a calibrated one, I can come over and make the comparison. Thanks.....
I can buy the calibration fluid on-line too, just dont' want to wait the shipping...
 
Pretty much talk to anyone near you that went to the last BAR swap. We handed out refractometer standard as well as some other goodies to all attendees.
 
in the absence of calibration fluid, you can use RO/DI water, it should read 1.000. (I assume you meant refractometer). Specific Gravity is linear, and it does not matter at what point on the scale you calibrate on.
 
RO/DI water will NOT calibrate your refractometer because of possible slope error. Granted the error will only make it off by 4 thousands at most, but the difference between 1.026 and 1.030 could do some damage.
 
I have heard the same theory as sfsuphysics mentioned, and it is very possible on this kind of instrument. I used the fresh water to test, it is 1 but it doesn't mean my reflector is not off at seawater level.
 
on a linear scale, if calibrating at 1.0000 does not give a correct reading at 1.025, then you got bigger problems to worry about. like you got a lousy refractometer. people confuse calibrating measures on a linear scale with calibrating measures on a non linear scale with reasoning exactly like the message above. calibrating say, a ph probe, which is on a "logarithmic" scale, is differnt from calibrating SG, which is on a straight linear scale.
 
Yes but on a pH meter you're calibrating against two points to figure out what you need (well the meter does that). While true sG is a linear scale as far as concentration, the mechanism for refracting light might not originally have been intended for salt water which many of the ones in our hobby are not made for, the "cheapy" $40 marinedepot one is such a one, the scale is still linear however the slope is higher.

The best result is to calibrate near the value you hope to measure rather than at some random value far away. This is calibration 101 with any instrument, regardless of how well made it is.
 
That is what I am going to do, I don't care it meaures the Ro/DI accurate or not. because I only use it to mix 1.026 salt water. I just need this point or small range be accurate. I only expect Yes or No answer from this reflectormeter instead of amount:)
 
DO NOT TRUST using RO/DI Water to calibrate your refractormeter. I had two different refractormeters and had both calibrated with DI water that tested to 18 mega ohm and they were both off by nearly 25% when tested at 1.026. These were not high end $100+ refractormeters but the typical ones you buy from DF&S or marinedepot.

I run my 600g FOWLR system at a salinity of 1.021. The fish like the low salinity and it saves me a fair amount of salt a month. Early this year my Hawaiian Dragon Eel stopped eating. I tried everything trying to figure out what was wrong and talked with multiple people that have kept eels for years. I finally lost him after about 2 months of this.

I thought it could be salinity but checked my refractormeters multiple times and everything looked fine. Right before he died I bought some Pinpoint calibration fluid and both my refractormeters were off by ~25%. So instead of my tank being at 1.021 like I thought it was it was at 1.015. I now keep calibration fluid around to check both of them every month or so and bought a pinpoint salinity monitor. Take this from me as an expensive lesson learned. :(
 
Lastduke I am over in San Ramon if you want to stop by and calibrate your refractometer this weekend. Its about time for me to do mine again. Let me know.

-Chris
 
Hi Chicken,

I also need my refractometer callibrated. I will be in San Ramon tomorrow at my daughter's soccer game.
Maybe you can help me out.

Thanks!
 
Chicken, thank you for offering help, I won't be avaialbe this weekend. I just ordered the pinpoint fluid, but need to wait for few days to get :(

Beto, if you are close to me, you are welcome to come over and use that to calibrate.
 
it goes without saying that if you use a bad fluid for calibration, your result will be bad. meaning using contaminated 53uS calibration fluid will give an inaccurate result just as if you used contaminated ro/di. I have always calibrated using 53 uS fluid, but always check using RO/DI and it has always been 1.00 perfectly.

The science behind the calibration is simple and straightforward, and it is very convenient to blame RO/DI as the culprit when it is in fact a user error causing the miscalibration, the same incorrect reading can happen if using contaminated 53uS fluid.

I never said calibration fluid is of no use. I merely suggested that "in the absense" of calibration fluid (say waiting 10 days for DFS to deliver), one can always use RO/DI.

The mark of a good salesman is the ability to sell you something you do not need. :)
 
I can show you two refractormeters, one from DF&S and one from Marine Depot that when are calibrated with 53 uS fluid show 1.005 when using DI water. I bought three bottles of pinpoint 53uS fluid from 2 different online vendors so I made sure I did not have bad calibration fluid (they all test within .001 of each other). I also am using nuclear grade DI resin in two freshly charged DI cartridges that test to 18 megaohm, so I know I have 0 TDS water. Some of these refractormeters are just not that well built. I would not have a problem spending $100 on one if I knew I could trust it but they all seem to be built to the same quality as the $40 ones. So for the time being I calibrate at 53uS and just run with that.
 
<a href=showthread.php?s=&postid=13762923#post13762923 target=_blank>Originally posted</a> by chicken
I can show you two refractormeters, one from DF&S and one from Marine Depot that when are calibrated with 53 uS fluid show 1.005 when using DI water. I bought three bottles of pinpoint 53uS fluid from 2 different online vendors so I made sure I did not have bad calibration fluid (they all test within .001 of each other). I also am using nuclear grade DI resin in two freshly charged DI cartridges that test to 18 megaohm, so I know I have 0 TDS water. Some of these refractormeters are just not that well built. I would not have a problem spending $100 on one if I knew I could trust it but they all seem to be built to the same quality as the $40 ones. So for the time being I calibrate at 53uS and just run with that.
Click to expand...

In your case, it does look like the water is the issue. (assuming the water used was room temp).
In my case, I know if I run out of 53uS fluid, I can use RO/DI to calibrate while waiting for fuild to arrive. In your case, since you know the difference is 0.005, you can always adjust the RO/DI reading by that value, in the remote case you run out of calibration fuild.

In case of emergency and you need to calibrate and find out you are out of 53uS fluid, and it is Sunday night and all stores are closed, you can use RO/DI to calibrate and offset by whaterever value you determined was the offset of the RO/DI.

The principle is still the same, and you can calibrate at any point in the scale, I probably should have said as long as you know the reference value of the fluid you use to calibrate. So if your RO/DI is 1.005, then you calibrate to 1.005.
 
<a href=showthread.php?s=&postid=13762879#post13762879 target=_blank>Originally posted</a> by d0ughb0y
The science behind the calibration is simple and straightforward, and it is very convenient to blame RO/DI as the culprit when it is in fact a user error causing the miscalibration, the same incorrect reading can happen if using contaminated 53uS fluid.
Click to expand...
Not to already beat this dead horse, but I never said teh RO/DI water is the culprit, I'm putting full blame on the refractometer. As you said the science being calibration is simple and straight forward, with most any tool it's best to calibrate around the numbers you're using in case there's a "shoddy" piece of equipment (in this case refractometers who's original purpose was not to test saltwater but perhaps some other fluid where the light bends differently).

I think in this hobby to put absolute faith in any particular tool is a bit fool hearty. I calibrated my refractometer once, doesn't mean I should trust it to be calibrated forever. As such, I have 35ppt solution sitting around and can test at a moment's notice.

But I think it's a fair bet to assume most probably don't have a refractometer that's perfect for seawater, as a result, by telling everyone you can simply use RO/DI water, most likely will yield wrong results.
 
Mike,

that was meant for chicken, which he/she clarified. I have also since revised my statement so it is not generalized to RO/DI, but simply any known reference fluid.
As calibraing with a 1.020 fluid would be just as good as calibrating with a 1.025 reference fluid. I think the variable was the RO/DI reference may be unknown, more likely than a problem with the refractometer, as chicken has mentioned, the $100 unit are very likely the same as the $40 unit, which I tend to agree since they all probably came out of the same factory.

cheers.

<a href=showthread.php?s=&postid=13763434#post13763434 target=_blank>Originally posted</a> by sfsuphysics
Not to already beat this dead horse, but I never said teh RO/DI water is the culprit, I'm putting full blame on the refractometer. As you said the science being calibration is simple and straight forward, with most any tool it's best to calibrate around the numbers you're using in case there's a "shoddy" piece of equipment (in this case refractometers who's original purpose was not to test saltwater but perhaps some other fluid where the light bends differently).

I think in this hobby to put absolute faith in any particular tool is a bit fool hearty. I calibrated my refractometer once, doesn't mean I should trust it to be calibrated forever. As such, I have 35ppt solution sitting around and can test at a moment's notice.

But I think it's a fair bet to assume most probably don't have a refractometer that's perfect for seawater, as a result, by telling everyone you can simply use RO/DI water, most likely will yield wrong results.
Click to expand...
 
Maybe a dumb question ... can you use water from the ocean/bay to calibrate? Even as a reference point. Like if I put ocean water on refractometer and note what it says, then just use that as a reference point to get ocean salinity?

I guess bay water doesn't work (Due to the freshwater flowing out of the delta) but ocean water should work, right?

OR...use the stuff we got from the last meeting ;)

V
 
”OR...use the stuff we got from the last meeting “

What's it?.........
I just bought the pinpoint fluid to verify my refractometer, it is accurate.
 
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