DIY inline refractometer

[chris2012]

I've just been working on a little attempt at using a normal refractometer 'inline' so that I can measure the brix
of the wort during mashing and sparging.

Today I just conducted a simple test heating water from around 17C to just below 70C before the pi crashed, I believe because of how I'd positioned it too close to the refractometer.

I'm going to redesign the prototype using triclamp fittings (2x 4-way triclamp fittings, with a sight glass on the end of one) in an effort to mitigate some slight leaks (note, the gland attached to the refractometer didn't seem to leak though).

I'm going to convert the blue line to a digital brix reading, using some simple image processing.

https://www.anfractuosity.com/projects/diy-inline-refractometer/

I also need to alter the shutter speed I set, as it gets too dark near the end of the video.

 

[IslandLizard]

An intriguing project!

Keep us updated, please.

 

[HiImBrian]

This is next level! I love the idea and can't wait to see the final working product.

 

[chris2012]

Thanks for the replies I think unfortunately I may have damaged the Pi by placing it so close to the refractometer as it got hot (at least that's the only reason I can currently think of for it not turning on now).

I'm currently looking at ordering a sight glass and triclamp tees, so that I can attach the refractometer through the sight glass and wrap an electroluminescent sheet around it, to also get more uniform lighting. (As I'm having a bit of trouble tracking the blue line using Python at the moment, due to some of the bright spots).

 

[SoulToast]

Thanks for the replies I think unfortunately I may have damaged the Pi by placing it so close to the refractometer as it got hot (at least that's the only reason I can currently think of for it not turning on now).

The USB connection point can be a little janky, and depending on your model, if the sd card isn't seated properly it won't boot.

One of mine has the sd card taped and clothespinned in because the holder broke just enough so the pins wouldn't contact.

Just a thought...

 

[chris2012]

Thanks I just gave the SD card a bit of a push and made sure the USB was pushed in, but no LED activity alas
I'll get another pi zero soon I think.

I just got a triclamp sightglass which the refractometer can sit in, however this is the cylinder type sight glass which is rather heavy!

I'm awaiting a small glass that looks like this https://www.glaciertanks.com/img-SGPV-G200-FKM-PTFE-1.JPG from China at the moment, which will attach to a cross with the refractometer at the other end of the cross.

 

[chris2012]

Just got some more parts:

I just found the thermowell is too big alas, so ordering a new one that's built into a 1.5" pipe with ferrules either end. So I can
do away with the top cross too.

Need to punch a hole in the triclamp blanking plate for the refractometer now.

 

[Deadserious]

Following

 

[kitr]

Very cool...

 

[Vale71]

Sorry for raining on your parade, but the scale will be completely off, possibly so much that getting a reading will be impossible. Your run of the mill refractometer is not design to operate as an immersion refractometer. It is designed so that you will get a reading matching the expected scale if light transitions through air-plastic cover-sample-prism in that order. If you immerse it light will just go through sample-prism and the angles won't match any more.

 

[chris2012]

You could well be right that it does affect it somewhat, but in a simple test I've done using the same distilled water, both read more or less bang on 0 brix. With the refractometer immersed in a glass, and with a sample reading with the 'lid' on.

Maybe it would affect it more when sugar is present?

What I'm also worried about is if the bimetallic strip might affect the reading too. And also the prism temp vs liquid temp.

I'm just waiting on a 1.5" blank now, and a hole saw to cut a 2.5" SS blank, before I can start getting some results.

What I can do during experiments is also compare small samples on a digital refractometer, to try to check accuracy.

 

[Vale71]

That could be a curious coincidence. I'd definitely do some extended testing with sugar solutions.
Immersion refractometers have been in use in breweries for some time in the last century before modern densitometers became widespread. Nowadays they are considered antiques. I've had a chance to try and use one, it was quite old and it was clearly very different from a handeld refractometer. It was much longer and the prism's angle was also different, all things that point at completely different design parameters than a handeld unit.

 

[chris2012]

I will definitely keep testing, with icing sugar in luke warm water, then stirring both gave almost exactly 1 brix.

And the same again for ~8 brix.

 

[cabron99]

Following!!

 

[etk29321]

Very curious to see if this works. I thought about doing something like this a few months back after seeing how much the sensors the guys on the automated brewing forum use cost. I'd thought about finding a square sight glass and mounting the prism on the outside.

 

[dyqik]

Sorry for raining on your parade, but the scale will be completely off, possibly so much that getting a reading will be impossible. Your run of the mill refractometer is not design to operate as an immersion refractometer. It is designed so that you will get a reading matching the expected scale if light transitions through air-plastic cover-sample-prism in that order. If you immerse it light will just go through sample-prism and the angles won't match any more.

I don't think that there'll be any significant issue. A cheap refractometer is designed to work so that you see light coming through the sample where the angle of incidence for rays going to the viewing point is less than the critical angle, and see reflected light from a blue screen where the angle of incidence is greater than the critical angle. The function of the sample cover is to provide diffuse uniform illumination through a sample of uniform thickness, so that the prism is uniformly illuminated.

As long as you can arrange that the light passing through the sample volume and reaching the prism is roughly uniformly illuminating the prism with diffuse light, it should read as normal.

 

[dyqik]

Very curious to see if this works. I thought about doing something like this a few months back after seeing how much the sensors the guys on the automated brewing forum use cost. I'd thought about finding a square sight glass and mounting the prism on the outside.

I was having thoughts about using a triclamp window with a system like the one described in this (now expired) patent. That system uses a flat glass panel, and a point source of diffuse light. I think grinding the triclamp window to give a ground glass screen (like an old-school camera focusing screen) will give a way to read the edge where the critical angle is reached, rather than using the diffusion layer in the patent. Getting enough resolution to detect the 0.03mm* per gravity point changes in the position of the edge might need a USB microscope or similar though.

* for 5mm thick borosilicate.

 

[dyqik]

Following through on this idea, I now have a $20 USB microscope, which can easily resolve 10μm features, and a few flat borosilicate 1.5" triclover endcaps and a tee being shipped from Still Dragon. I'll need an LED with a pinhole mask in front of it. First test will be with some scotch tape on the glass rather than grinding it.

 

[christian86]

Maybe id you discover how one of these works

https://www.amazon.com/-/pt/dp/B007...s=digital+refractometer&qid=1601172563&sr=8-3
never use one of these digital, it seems it dont need a plastic to be putted on top of the liquid for the angle of light, like the handled versions...