Milwaukee Digital Refractometer MA887

[7hogwarts]

I thought I would share this inquiry I sent to Milwaukee Instruments .

I hope someone can shed some light on the differences between saltwater (Natural vs synthetic)
1.025 vs 1.028/ 35ppt.

"To: [email protected]

Recently, I decided to check two Milwaukee digital refractometers. They were initially in two different rooms that were a couple degrees different in temp. anyway, I brought them side by side, turned them on, zeroed them both with the same RODI water. I used 35ppt to check them. One unit read1.028 SG,
the other read 1.027. Once I allowed both units to acclimate to the same room temp they both read 1.028. Aren't the units supposed to automatically adjust for temperature differences? And yet when I switched the units to PPT they both read 35PPT. Not 1.026 in the SG mode. What's going on? Any help?"

The reply I received promptly back from Milwaukee Instrumets

"First clean the base lens with Windex using a heavy soaked Q-Tip- Then flush the windexout of the pan byusing the pipette we provide with "SteamDistilled Water" & do 2 or 3 loads of the pan and extract the distilled water using the pipette (you MUST use "Steam Distilled Water" ) and then-- load the pan 1/2 way with "steam distilled water" (you can't use RO or DI water for this unit) and press "zero" by doing this you are sure no residual or refraction material is on the lens-

You should be using Seawater validation solution provided with your unit. @(1.025 SG)- Never use conductivity calibration solution. The reason is that Conductivity probes, like the Neptune and Pinpoint, are designed for NaCl testing and not Seawater. Most "validation" liquids for refractometers are made from Sodium Chloride [NaCl] @ 99%- one of the providers of this on the internet is Sybon Scientific and there are others. The problem with their solution is that it is designed for Salinity validation not for Seawater. Their Sodium Chloride [NaCl] @ 99% and seawater is made up of Sodium Chloride [NaCl] @97% and Potassium Chloride[KCl] @2% and Other Trace Mineral Salts@1% and that 3% makes a huge difference.

Using this popular salinity liquid sellers, Sybon's,own chart http://www.premiumaquatics.com/prodimages/tropicden/Sybon_refracto_cal_solution.jpg you will see that their solution is rated at 35 ppt of Sodium Chloride and has a SG of 1.0264SG and 53mS/cm@77F which is their target for their salinity measurement units but that is for "Salinity Meters, Testers & Refractometers" not Seawater and their primary target is PT/PSU or mS/cm. However, the optimum target for seawater aquarium is 1.025 at PPTof@ between 68' F to 72'F(20/20). --this brings up a point that all of this should be done at 70F not 77F

The only way to validate your unit is with an independent actual seawater solutionkit however if you are at+/- 0.001 SG you are within the units accuracy specification.- If you do not have a validation kit we will be glad to send a kit to you at no charge."

I replied-

"Thank You for your quick reply. I do have some concerns/questions though. When I read the instruction manual for MA887 unit it does state that"Samples are measured after a simple user calibration with distilled or deionized water" No where in the instruction manual do I see that Steam distilled water must be used. (My ignorance, but i don't know else you would distill water.) Nor do I see that I should use Windex to clean the lens. Perhaps there is an updated manual. Also, my unit did not come with any calibration fluid. I do not know if my friend's unit came with any calibration fluid either. The calibration fluid I used is being produced by Julian Sprung's company Two Little Fishes. I'm not sure of his calibration fluids source.

If I use seawater calibration fluid, I should see the MA887 calibrate to 35PPT/1.025SG?"

"I just checked the Julian Sprung calibration product Accurasea. It too is a natural seawater product that has been sterilized and adjusted to 35 PPT at 77 degrees.
I forgot to also mention in the previos email, why would the MA887 show 35PPT and still have a 1.028 SG? I'm still confused, are they actually two different measurements?"

I received no reply from Milwaukee. It's been 2 weeks.

So if someone can shed more light on the differences between the saltwaters and differences of SG/PPT. Should my refractometer read 1.025 or 35PPT in my aquarium?

Thanks in advance!

 

[Salt It Away]

I have had the same problems with this unit. The provided 35ppt provided solution has never read 35. I did use the steam distilled water packed with the meter. I have cleaned, re-cleaned the lens and taken the unit into warmer areas, etc. Discouraged.

 

[KingTriton]

VeeGee STX-3 > MA887

 

[William Bunton]

I've had two MA887s go bad. The first one started reading very low (1.021 using the calibration fluid they sent me, after zeroing with the distilled water they sent me). The replacement one day decided I had an airgap and hasn't worked since. I really like the VeeGee STX-3 I got to replace my BRS (nothing wrong with the BRS, but my old eyes fine the VeeGee _much_ easier to read).

 

[Randy Holmes-Farley]

FWIW, some of what they replied to you is wrong, but I'm not sure what you are really trying to clarify.

It is certainly true that a sodium chloride solution that is exactly 35 ppt will not have the same properties as a seawater solution at 35 ppt. Not refractive index, not conductivity, and not density/specific gravity.

But one can make sodium chloride solutions that exactly match the refractive index of 35 ppt seawater, and that is included in my refractometer article:

Refractometers And Salinity Measurement
http://www.reefedition.com/refractometers-salinity-measurement/

 

[Randy Holmes-Farley]

For calibration of their device, any type of distilled or RO/DI water is perfectly suitable, assuming it is reasonably pure.

You can then check it on a 35 ppt standard if you want, and when I say 35 ppt, that means (and is the case commercially as well) a standard that matches the refractive index properties of 35 ppt seawater, no matter what is is made of.

 

[Randy Holmes-Farley]

FWIW, I'm shocked and disappointed at how incredibly WRONG their email is. Makes me much less impressed with them, despite having a quality device.

"Their Sodium Chloride [NaCl] @ 99% and seawater is made up of Sodium Chloride [NaCl] @97% and Potassium Chloride[KCl] @2% and Other Trace Mineral Salts@1% and that 3% makes a huge difference."

In reality, seawater is roughly

54% chloride
30% sodium
7.7% sulfate
3.7% magnesium
1.2% calcium
1.1% potassium
and on down the line

 

[7hogwarts]

Thanks for your replies. By Milwaukee's reply I was feeling really confused. The MA887 I thought should read 35PPT /1.026SG consistantly. Not vary to 35PPT/1.028. My problem I guess is that I was looking at PPT/SG were constant. Kind of the way Farenheit/Celcius. All of this then makes me wonder should every salt have a variable reading since different manufacturers have different chemical make ups? Or is it too fine of a line to be concerned?
Bottom line should my saltwater be adjusted to 35 PPT or 1.026 SG?

 

[Randy Holmes-Farley]

Thanks for your replies. By Milwaukee's reply I was feeling really confused. The MA887 I thought should read 35PPT /1.026SG consistantly. Not vary to 35PPT/1.028. My problem I guess is that I was looking at PPT/SG were constant. Kind of the way Farenheit/Celcius. All of this then makes me wonder should every salt have a variable reading since different manufacturers have different chemical make ups? Or is it too fine of a line to be concerned?
Bottom line should my saltwater be adjusted to 35 PPT or 1.026 SG?

While the chemical makeup of salt mixes can be a concern for other reasons, I have shown in various articles that the methods we use for salinity determination are not unduly impacted by the variations in chemistry we normally see.

Let's back up a bit.

The Milwaukee should be "calibrated" with pure fresh water of some sort (distilled, RO/DI, etc.).

You need not do anything else in order to be able to measure seawater salinity/specific gravity with it.

If you check it with a "35 ppt" seawater standard that is suitable for refractive index devices, it should read 35 ppt or sg = 1.0264. While I've not used this unit, I don't believe you "set" anything at this point. It is just a confirmation.

Suitable fluids for this purpose are my DIY (from the article), Pinpoint 53 mS/cm fluid (it is not just sodium chloride, but a seawater mimic), and likely many other brands.

Whether you choose to interpret/report your measurements in specific gravity or in salinity (ppt) doesn't really matter.

 

[Waters]

For what its worth, I have always had inconsistent readings with mine to the point where I can test the water twice, back to back, and get two different readings. I thought these were supposed to be one of the more accurate devices available to the hobby? I have always followed directions in regards to calibrating and testing. Mine was not packaged with any calibration fluid either.

 

[KingTriton]

Mine was always consistent with the calibration fluid yet inconsistent with NSW. I would continuously retest the same water twice and get different results.

 

[sghera64]

FWIW, I have the MA887 from Milwaukee. I can 'rezero' it (s.g. = 1.000) with bottle of steam distilled fluid Milwaukee sent with it. When I read my RO water, I also get s.g. = 1.000. So, I conclude that RO water can be used to 'zero' the instrument.

However, I have a bottle of 35ppt solution that Milwaukee sent with the unit and one that I bought from BRS. The MA887 cannot be 'calibrated' for non-zero readings. It can only be 'zeroed'. I was troubled that my instrument was hopelessly "off" in the range that I use it for measurements. I was also wondering if my bottles of 35ppt calibration solution were "off". They were a couple of years old. They were opened maybe 1-3 times and they were not off the same amount between them. I was enthusiastically skeptical of the "calibration" solutions.


I read Randy's post about the NaCl standard that can be made which he found in his CRC handbook. I followed his instructions and here is what happened:

Milwaukee Digital Refractometer non-zero reading check.

1. Made standard solution using 3.65% Morton iodized salt solution:
   1. 1.825 g +/- 0.005 gm NaCl using a My_Weight i101 analytical balance.
   2. 48.175 g +/- 0.005 gm RO water using i101 analytical balance.
      
2. Calibrated the refractometer to 1.000 using Naslow Chemical Ltd Steam Distilled Water for calibration.
   
   
3. Made 4 readings using the 3.65% NaCl solution. Results were:
   1. 1.026 s.g
   2. 1.027 s.g *
   3. 1.026 s.g.
   4. 1.026 s.g.
      
4. Observations:
   1. For tests a, c. and d. the sample was removed, the lens rinsed with RO water 3 times and then blotted and gently wiped with a soft clean cotton cloth.
   2. For test b, the sample was removed and the lens was rinse with RO water 2 times. It was not blotted/wiped with a cloth.

This tells me that my MA887 is likely giving me truthful readings in the 1.026 s.g. range within its stated +/- 0.001 s.g. accuracy. It also suggests that the procedure Randy outlines is a good method to provide a check of the MA887 digital refractometer's accuracy in ranges above zero. Unfortunately, if the MA887 ever begins to read more than +/- 0.001 s.g. of the NaCl check solution, there is no adjustments designed into the instrument to correct for it. One would have to make a calibration curve of 2-3 points within the target range and then manually correct the numbers.