dukeja wrote:We are good here. In terms of coffee, whatever float the boat works. :)

I only have the 0~40% Brix reader at hand, and I have no problem reading it at 0.1% by eye. (even my eyes are pretty bad now) The 10% Brix reader will be even easier to read. Using a light moving around the flat top side to change the illumination angle will help to identify a very sharp edge, which is the boundary formed by the critical angle.

I have no need to use machine vision yet, but if there is enough interest I'll try my Raspberry Pi camera to make a demo. I'll also try to run some Zemax simulation that may come out some low-cost lens solution to replace the existing one. As I said, it is fun toy to play with.

If you can reliably read between the lines, and the refractometer actually produces repeatable results, then a ±0.05°Bx error is usable, especially given the price point of the device. But there are some ifs there.

For espresso an inexpensive handheld optical refractometer makes a little more sense since the concentration is on the order of ten times greater. A precision of 0.1°Bx isn't bad at all, never mind half that if possible. I wasn't interested in one of these things when I was making brewed coffee. But now that I have an espresso machine I may buy one of these and see how well it actually works. They sell a 0-18°Bx version with 0.1° rulings. For $30 it's worth a try.

TDS is the concentration of coffee in each sip....it's the enjoyment factor;
Extraction yield is the total amount of caffeine in my body after finishing the entire cup....it's the buzz factor or pee factor (or both);

QED

jmotzi wrote:TDS is the concentration of coffee in each sip....it's the enjoyment factor;
Extraction yield is the total amount of caffeine in my body after finishing the entire cup....it's the buzz factor or pee factor (or both);

You got it!

Amazon now kept slipping on its delivery time, so called 2-day is often 3-day and at the very end of the day, like 10pm..

But I did get the 10% Brix refractometer. The sensor head does seem to be much heavier (claimed to be copper). In comparison, my first 40% Brix unit is definitely made of aluminum. And I can see that in the test result, the "copper" head reached temperature equilibrium much faster and gave me more trustworthy result.

However, when I peek into the scope, I was quite disappointed. The 10% full scale in length (or angular space) is only about half of the 40% scale, which makes it effective only 20% brix full-scale one, if that makes sense. Also, I don't think they use any higher refractive index prism to enhance the response, so the response is about the same but only using higher mag. optics to amplify the reading, which make the blue/white section line blurrier. And the illumination angle is a lot more trickier to get right. In the end, this new unit is probably only 1.5~2x better in resolution. However, the copper head does make it worthy.

I got to test both this morning with my 3-day-after-roaste Guatemala Asodiett Txol Xa'Q at Citi+. Beans were grounded by Ditting KR805 at 5.0. Just the blooming in V60 already blew me away, and even my wife can smell it upstairs. It was quite sweet and floral smell that I rarely detect in my brewing process. 10g bean with 180g water and all drained out in 2:05. It was a very delicious, bright, and tasty cup. Copper head measured 1.5% Brix, which was 1.275% TDS and the E.Y. was 19.5%. In comparison the aluminum head measured lower at the same time (, which is often due to temperature difference) and is harder to tell.

My second cup used the setting of 4.5 on Ditting and exactly same V60 brewing profile. And the drain down time was about the same. That is what Ditting keeps amazing me. Even at very fine setting, the flow is never stalled by fines. This cup tasted more mature than the previous one. It was slightly leaning toward bitterness and yet has more sweetness. I don't know how that would be possible, but apparently the coffee was extracted more.

And the copper head quickly verified it. I got 1.6% Brix (TDS: 1.36 and E.Y: 20.8%, if I cut off at 153g like I did last time). Again, aluminum head measurement was fussier and I have to "feel" the difference. In the end, I will call the copper head very effective in guiding my V60 brewing.

dukeja wrote:Copper head measured 1.5% Brix, which was 1.275% TDS and the E.Y. was 19.5%.

It looks like you're just multiplying by 0.85. That's not a very good conversion formula. 1.5° Brix is equal to 1.20% TDS. Saying 1.275% is not just off by a significant margin, it's overstating the precision by two orders of magnitude. It seems a lot more likely that you can say 1.2 ± 0.1% TDS. And that would mean your E.Y. is 18.4 ± 1.5%. Maybe.

Can you really use some sort of secret sauce to coax more out of it than it's low price would suggest is possible? I can't help but think that there must be a good reason why an optical refractometer that looks similar and has the same range and resolution would cost $200 instead of $27. I'd love to be wrong. Show me the beef!

jpender wrote: It looks like you're just multiplying by 0.85. That's not a very good conversion formula. 1.5° Brix is equal to 1.20% TDS. Saying 1.275% is not just off by a significant margin, it's overstating the precision by two orders of magnitude. It seems a lot more likely that you can say 1.2 ± 0.1% TDS. And that would mean your E.Y. is 18.4 ± 1.5%. Maybe.

Can you taste the difference to the resolution that you are asking for? To me the measurement serves a certain purpose, and if the measurement can help me dial in grinding setting on Ditting from 4.5 to 5, I will be impressed. That is exactly what I am looking for. I am not sure your goal so this reference may not suitable for you.

jpender wrote: Can you really use some sort of secret sauce to coax more out of it than it's low price would suggest is possible? I can't help but think that there must be a good reason why an optical refractometer that looks similar and has the same range and resolution would cost $200 instead of $27. I'd love to be wrong. Show me the beef!

I would image that the electronic ones may be based on the same principle. And $200 is easily justifiable. You need to pay extra electronic parts, assembly cost, marketing, etc. If you are like me, certain you can conjure up some patentable idea that can measure easily 1E-6, but the optics and light source will be far greater than $200. If you look into the optical prism and lenses from Edmund Optics or Thorlabs, you will be grateful for the $200 final cost.

Just did another V60 brewing with my recent El Salvador Santa Ana Pacas AA. Same story, I tried Ditting at 4.75 and taste a little bit "muted". I felt that there should be more flavor to be released. Yet at the same time I don't want over-extract it. Copper head told me 1.5% Brix and from the experience I had so far I knew that there may be some room to push.

So I tried Ditting grinding setting on 4.25. The cup is more rich in flavor. Test it again and I got 1.7%, which is pretty close to the top limit. My experience with some Ethiopia beans was that 1.8% Brix will start to show some hint of over-extraction. For this bean it may not applied, but at least now I have some guideline to navigate. These notes will help me to explore the full potential of the beans.

Another example is how I use Brix measurement to realize the effect of V60 pouring mechanics. By pouring facilitating the center flow or not, I got quite a bit Brix difference (which is R.I. difference to be exact). And that is exactly what I am looking for. I would be happy to pay for this $30 gadget without dragging my laser source with optical mounts and worry about coupling to the resonator at the same time. That is just not practical.

dukeja wrote:Can you taste the difference to the resolution that you are asking for? To me the measurement serves a certain purpose, and if the measurement can help me dial in grinding setting on Ditting from 4.5 to 5, I will be impressed. That is exactly what I am looking for. I am not sure your goal so this reference may not suitable for you.

I don't have a refractometer so what I can taste is irrelevant. The question I had earlier was simply: What precision can you achieve with this thing? You said that there is "some technique needed to enhance the reading in addition to the temperature, such as illumination angle control, viewing angle, or if you could have some camera doing the machine vision for you." So I asked, and I'm still wondering, what is it you do exactly? And what precision can you actually achieve?

If your point is that it's good enough as is, out of the box, for your purposes, whatever they are, then there's nothing more to say.

jpender wrote: I don't have a refractometer so what I can taste is irrelevant. The question I had earlier was simply: What precision can you achieve with this thing? You said that there is "some technique needed to enhance the reading in addition to the temperature, such as illumination angle control, viewing angle, or if you could have some camera doing the machine vision for you." So I asked, and I'm still wondering, what is it you do exactly? And what precision can you actually achieve?

If your point is that it's good enough as is, out of the box, for your purposes, whatever they are, then there's nothing more to say.

Yes, I realized that I do own you this answer. So here we go.
I can tell the difference of 1.55 and 1.5% Brix, so the minimum resolution is 0.05% Brix, which is about 0.4% TDS by my eye. Someone with younger eye probably can do slightly better than that.

And this is the limitation of copper head's implementation. If I ever had a chance to get some ideal glass, I may be able to improve the sensitivity 4x with the same design.

dukeja wrote:I can tell the difference of 1.55 and 1.5% Brix, so the minimum resolution is 0.05% Brix, which is about 0.4% TDS by my eye. Someone with younger eye probably can do slightly better than that.

Thank you for that. But the reading resolution isn't necessarily equivalent to the measurement precision. If you measure ten samples from the same coffee what do you get? And what else, besides squinting, do you do? For example, do you attempt to equalize the sample and device to 20°C?