digital vs naked eye you decide

[Aqua-Digital]

We recently started looking into developing another Aqua Digital product - a hand held digital refractometer using conductivity instead of prism.

The fore and against we see as this

the Fore - easy to read, highly accurate
the against - needs calibrating everytime, although a one touch event.
Peoples built in feeling nothing is better than a refractometer

Ok to pick up on this argument - How many out there really are aware 99% of refractometers are designed to read NACL not NSW? The difference being NACL has no impurities or added minerals that throw out the reading, this is why unless you have a dedicated NSW refractometer, they must be calibrated to a known and trust NSW solution such as pinpoints. Through support we come across a massive amount of lack of education in this.

The concern is how many do not do this and have innacurate salinity readings in their tank? This is the biggest support question we get when clients install expensive salinity probes from GHL and get a different reading, and the reason we are considering the digital approach.

So my question to the community is this - Would you trust a digital reader that can only read what is the correct salinity even if it differs from you old NACL refractometer. Or would we get multiple support argumetns over the reading from what people have learned to accept as correct (when on most cases it is not)

We would love to bring these to market but feel that the hobby is too biased towards what has become standard.

Your feedback is important.

[Mike-fish]

I wasn't aware that our refractometer looked at a different compound

[Aqua-Digital]

Most Refracts are designed for NACL we are only interested in NSW, this is only an issue with prism refractometers.

Refractometers read by light refraction and this refraction is read by a scale on the glass.

Digital read the conductance of the water thus not effected by impurities or minerals so as accurate whether NSW or NACL

[sphelps]

Personally I think such a device would be a waist of money.

1 - I'm yet to meet anyone overly concerned regarding inaccurate salinity levels in their tank if they are already using a refractometer.

2 - Anyone overly concerned regarding inaccuracy of an NACL refractometer only needs to calibrate it once using natural seawater to verify it's accuracy. Once verified or even adjusted if it is way out the meter is now completely accurate.

3 - In my own personal testing my refractometer measures natural seawater perfectly accurate even calibrated with RO water. I've had this meter for years, it was over expensive ($50) and referred to as salinity refractometer.

4 - The resent outburst of concern regarding inaccurate refractometers seems more of a myth (exaggerated from fact) and now many companies are releasing new seawater refractometers, some digital some not but always with the promise of more accuracy and a significantly higher price tag. It just seems more of a marketing ploy to me.

5 - The only reason I would spend more on a digital device is if it would make things easier. However refractometers are already very easy and just the fact that you would have to calibrate it every time is enough to dismiss any gain from accuracy which I don't even believe is there. Conductivity meters are also prone to many errors as well, more so than a standard refractometer.

[Cal_stir]

Originally Posted by sphelps

Personally I think such a device would be a waist of money.

1 - I'm yet to meet anyone overly concerned regarding inaccurate salinity levels in their tank if they are already using a refractometer.

2 - Anyone overly concerned regarding inaccuracy of an NACL refractometer only needs to calibrate it once using natural seawater to verify it's accuracy. Once verified or even adjusted if it is way out the meter is now completely accurate.

3 - In my own personal testing my refractometer measures natural seawater perfectly accurate even calibrated with RO water. I've had this meter for years, it was over expensive ($50) and referred to as salinity refractometer.

4 - The resent outburst of concern regarding inaccurate refractometers seems more of a myth (exaggerated from fact) and now many companies are releasing new seawater refractometers, some digital some not but always with the promise of more accuracy and a significantly higher price tag. It just seems more of a marketing ploy to me.

5 - The only reason I would spend more on a digital device is if it would make things easier. However refractometers are already very easy and just the fact that you would have to calibrate it every time is enough to dismiss any gain from accuracy which I don't even believe is there. Conductivity meters are also prone to many errors as well, more so than a standard refractometer.

+1, if my refractometer is out 1/10 of 1 point, so what, everybody runs their systems at a different salinity, there is even variations in different areas of different oceans, the main thing is that they are consistant, big deal if i think my salinity is 1.025 but it is actually 1.024, as long as it is consistant.

[Aqua-Digital]

REMEMBER - This thread is driven by your input, not me trying to sell you something else, its here for us to gauge viability of a new product.

My only sub point on this is the highlight that a refractomer should be calibrated to NSW, but thats a sub argument to the main point of the thread.

[rayjay]

Originally Posted by sphelps

4 - The resent outburst of concern regarding inaccurate refractometers seems more of a myth (exaggerated from fact) and now many companies are releasing new seawater refractometers, some digital some not but always with the promise of more accuracy and a significantly higher price tag. It just seems more of a marketing ploy to me.

Is this comment based on any documented evidence or just your personal experience along with the few others that have reported the same?
At least for the point of view that a seawater and a NaCl refractometer produce different results, there is documentation out there, and the fact that Dr Randy Holmes-Farley confirms that it is different, then that is more convincing to me than a hobbyist's anecdotes.
Randy has tested many refractometers and found errant results from many so those particular ones are only accurate at the range they are calibrated for.
This can be true even for seawater refractometers. Generally, but not exclusively, the higher priced ones will be more likely to be more accurate.
Maybe your refractometer is an errant NaCl refractometer that just lucked in to be errant in a way as to be accurate through the range. Like I said before though, it's impossible for an NaCl refractometer and a seawater refractometer with true prisms respectively, to give the same results throughout the scale even if both are calibrated with the same calibration fluid. The refracting prisms in each case are different.
The shortest explanation of how they work should suffice and can be found at Refractometry Theory and Abbe Refractometer
Also, while inaccuracies can exist in conductivity meters as well as refractometers, science basically uses conductivity over refraction as they prove to be more reliably accurate.

This link is merely an "interest" link some might find interesting, especially if they teach school. Refractometer

[Mike-fish]

Would these digital one be temperature compensated

[rayjay]

First of all, if it no longer involves prizms, it will no longer be a refractometer IMO. It will then be a conductivity meter.
Randy Holmes-Farley has many articles explaining that the standard refractometer is only accurate for NaCl, or, when calibrated with a calibration fluid, only accurate at that specific range.
It's amazing how many people with a standard refractometer swear up and down that their refractometer is accurate with using water to calibrate as well as using calibration fluid. The only way this is possible is when using a seawater refractometer.
Randy on Refractometers and Salinity
This is his Archived Article on using Conductivity to Measure Salinity
Randy on Home Made Calibration Standards Including Conductivity

All that being said, I still use my SeaTest swing arm hydrometers that I started with over 18 years ago. I check them about once a year against my certified calibrated hydrometer from Fisher Scientific and it is always on.
I rinse after every use and soak overnight in vinegar once a week.

[Mike-fish]

With the traditional refractometers how much of an error factor are we talking about nacl - NSW