Using electronic scales for running gravity reading

[Econwatson]

If all you were wanting to do is find out the alcohol content, I always thought it would be cool if you could modify a breathaliser, and get an alcohol reading that way.

 

[RdeVjun]

Beaten by MB, nevertheless IMO your most worthwhile solution is probably in densimetry. Unfortunately gross mass and volume sensing at this scale can be fiddly, it can be susceptible to environmental fluctuations such as temperature, humidity and electrical noise, plus accounting for evaporation and respiration is difficult, and that's presuming you can source affordable sensors and interface with the required precision.
Yes, densimetry would also have value in the mash and boil, so a solution could be more universal than just monitoring the ferment.

The Beerbug could be helpful- hope it doesn't rain on your parade too much?

This bubble counter might also be useful if you're wanting to monitor respiration rate, I never pursued it after seeing the light with cling film displacing my airlock bubblers.

In my day job we explored densimetry for continuous monitoring of suspended sediment in waterways, but sadly it never got very far off the drawing board due to the expense and experimental nature- for a short term project we couldn't risk the time it would take to develop a solution, so just reverted to conventional pumping samplers and event sampling etc., however I still feel it has some merit, particularly where remoteness or access is an issue.

HTH!

 

[schrodinger]

So here are some numbers for the OP to chew on. If your wort had the equivalent of 4 kg DME in 20 L, the total mass loss as CO2 assuming 100% attenuation would be around 2kg, or 10% of the total mass. For a more realistic 70% attenuation, it's around 7%. So if your scale's precision is around 0.5% of full scale, and supposing it goes up to 50 kg, your daily change for a 7-day ferment would be approximately equal to the scale's precision.

Edit: I stuffed up the other calcs!

 

[MastersBrewery]

Beaten by MB, nevertheless IMO your most worthwhile solution is probably in densimetry. Unfortunately gross mass and volume sensing at this scale can be fiddly, it can be susceptible to environmental fluctuations such as temperature, humidity and electrical noise, plus accounting for evaporation and respiration is difficult, and that's presuming you can source affordable sensors and interface with the required precision.
Yes, densimetry would also have value in the mash and boil, so a solution could be more universal than just monitoring the ferment.

The Beerbug could be helpful- hope it doesn't rain on your parade too much?

This bubble counter might also be useful if you're wanting to monitor respiration rate, I never pursued it after seeing the light with cling film displacing my airlock bubblers.

In my day job we explored densimetry for continuous monitoring of suspended sediment in waterways, but sadly it never got very far off the drawing board due to the expense and experimental nature- for a short term project we couldn't risk the time it would take to develop a solution, so just reverted to conventional pumping samplers and event sampling etc., however I still feel it has some merit, particularly where remoteness or access is an issue.

HTH!

Unfortunately Beerbug won't hold pressure, and calcs for escaping Co2 would really be come complex if we start presurising things at different temps, so densimetry or refraction are the only 2 methods I can see working

 

[MHB]

Someone asked about this in the shop today. Had a bit of a think about it, the best solution I can come up with is to put a largish volume not too heavy sinker on a tether and suspend it in the brew from a load cell.
Archimedes worked this one out about 2000 years ago
Just to think through the process –
Say we took a bottle that was 1L and added filled it with sand until it just sank, i.e. massed 1.1Kg
Hang that from a scale with a thin thread (most modern lab balances have a hanging hook underneath and a USB or RS232 port)
In air the scale would read 1.1 Kg
Put it in water and it should read 0.1 Kg as it has displaced 1 L of water
Put it in 1.050 wort and it will read 0.95238 Kg (if it was exactly 1 L)
As the gravity falls you get les buoyancy so the apparent mass increases and moves back toward 0.1 Kg.
If you took a piece of stainless pipe and welded hemispherical ends on and tacked a length of fine SS TIG wire to supply the tether, (given you can weld) you would have a food grade, easy to sterilise sinker.
Naturally the bigger the volume of the sinker and the closer its density is to the wort the easier it is going to be to get accurate results, but you can get a 0.0001g scale for not much these days, if this is a uni project you could probably borrow one from the Chemistry department.
Mark

 

[ArgM]

Hey MHB,

Yeah, I had that thought as I was going to bed last night that displacement and something to read the level of displacement should work... I can barely weld, but I'm sure I could give it a shot, can always use the practice! I guess I'd have to measure the mash at timed intervals manually as my pot isn't too big, but I'm in there cooking it anyway so no extra effort... I feel like a bubble counter would be a cool addition RdeVjun.
Talked to the lecturer today about it and it sounds like I won't be able to tailor the subject around it but any work done on it will be considered for additional credit! Which is pretty good considering Im recovering from a back injury and only doing that one subject this semester.

I might start another thread about this set of sensors and what information people deem important information and collecting and displaying the info, or we could tack it onto the end of this one? not sure about the semi off-topic thread roles!

 

[MastersBrewery]

the problem being you would have to recalibrate for each batch or be dead accurate with batch volume to achieve repeatability, or have I missed something?

 

[MastersBrewery]

Found this also Link though bubbles forming on the sensor may throw it out some as stated worth a try though

 

[schrodinger]

...calcs for escaping Co2 would really be come complex if we start presurising things at different temps...

Why? CO2 loss = [CO2 concentration difference (e.g., micromoles CO2/mol air, i.e., ppm)] X [flow rate (e.g., mol air/minute)]. If flow is measured on a volume basis, it's easy to correct for pressure and temperature (moles/volume = n/V = P/RT). And since CO2 conc in the fermenter will very rapidly reach 100% whereas CO2 outside is negligible (~400 ppm), you could get away with only measuring flow rate.

 

[ArgM]

Yeah, I didn't think about the calibration, would be near impossible during mash/boil where the volume is constantly changing...
Im beginning to wonder if looking at gravity might be the wrong way to go...

I've been playing the idea out in my head of using a sensor similar to the one diabetics take blood sugar tests on to read the level of sugar, as the beer ferments or mashes this sugar level should change, if I can match OG and sugar level at start of brew and FG and sugar level at end of brew I could then use the information for the sugar level in between as an indication of what the specific gravity was at a certain time. I could also take a SG reading randomly during fermentation and use this as a test reading?

 

[ArgM]

Does anyone here have any experience with using a Ultrasonic Transducer?

"Ultrasonic waves are passed from a source, through the fluid of interest, and into a detector which measures the acoustic spectroscopy of the waves. Fluid properties such as density and viscosity can be inferred from the spectrum." http://en.wikipedia.org/wiki/Specific_gravity

There also seems to be a few Arduino compatible sensors and tutorials on setting one up... It seems like this would be a good way of doing, only downside will be translating the information into SG which Im sure will become easier with time

 

[MastersBrewery]

I would think once you had spectrum differential across a sample of differing gravity "worts" a simple equation would spit out the SG all done on the arduino

 

[ArgM]

True, this is looking like the way to go, found the sensor online for $6 so I reckon it's worth a shot!

Thanks everyone for your ideas and experience!

Going to start a post documenting my process as I go through and put it all together, so if you wanna check out how it goes look that up!

(probably get started in a week or so)

 

[MastersBrewery]

I did see a link to a paper on the subject of ultra sound and liquid density, they wanted $35 for me to read it you may find you will need to play with a range of frequencies and returns to get one reading. Be very interested in your results, don't forget temperature variance.

 

[MCHammo]

I started working on something to do exactly this; measure wort density using ultrasonic sensors. I got most of the way there, but gave up at the end for several reasons (one of which is that it isn't really necessary)

1. You need the longest possible path through the liquid to take measurements, as the time difference between two different densities is incredibly small. On that note,
2. You need very accurate, high resolution timing to even detect the differences.
3. The sensor will need to be immersed in the wort to accurately measure the path through the wort. The sensors need to be resistant to water, alcohol, etc. (such sensors do exist)
4. Some US sensors (particularly these resistant ones) need a high driving voltage to operate. This presents its own problem with regards to driving circuitry (and propagation time through the circuitry). The sensors I tried needed 140Vpp to operate properly (and work at 40kHz). For that, I needed to construct a transformer to step 12V up to 140V.
5. The ultrasonic waves that you intend to send through the liquid will also travel through the container. They do so faster than through the wort, so you need to do some very smart filtering
6. The US waves do not like to reflect off a surface in the FV (at least in a plastic FV), so you need two opposed sensors.
7. Fermentation activity inside the FV will affect the time of flight of the US waves - suspended yeast, CO2 bubbles, turbulence, etc will throw off the readings.
8. As mentioned, temperature will affect the density of the wort. That's a relatively easy thing to measure and calibrate for, though.

I might have missed a few things, that's just off the top of my head.

Masters, can you give us a link to that paper? With any luck, my uni has a subscription to that publication and I can have a read of it myself

 

[MastersBrewery]

MCHammo, it was a late night of trawling a week or 2 back, will see if I can retrace my steps to night

 

[TheWiggman]

My experience with ultrasonic transducers is with solids, specifically thickeness measurements. MCHammo has covered everything I might be able to go on about - the variable you will be measuring is density. Typically for industrial application the speed of sound through a solid will range from 1500 - 9000m/s. You can get pretty accurate measurements off the time it takes to reflect the signal, which for a ceramic 5mm thick can be around 6 E -7 seconds. They will measure accurately to within +/-0.1mm if calibrated correctly. Albeit with a unit that costs thousands of dollars.

Water is around 1400 m/s (temp dependent). You could back-calculate from your result knowing the bulk modulous and time it takes to reflect off something in the wort. The biggest variance, in my opinion, will be the target you will be reflecting the sound off as it this isn't REALLY accurately set up your results will be inconsistent and innaccurate, unless you knew the SG and temp to start with and tell the controller 'this is equal to this SG'. The distance could then be calculated and the rest of the work done from there. Of course like MCHammo said your sensor would be immersed which is not ideal.

Otherwise, for much more effort, you could place the target (say a stainless plate) in the bottom of the wort and have the sensor pointing at the solution from just under the lid. The biggest issue you'll face there is massive reflections from the suface of the water which will have to be somehow ignored, which is typically done using some sory of clever algorithm or graphing the results and determining which reflections should be considered. You then have two things to account for, being air and wort. And krasuen too I suppose.

I think MHB's suggestion is the best. There's more than one way to skin that cat.

 

[MCHammo]

The setup I was going for two sensors (one Rx, one Tx) set in the walls of the fermenter, one on either side. That takes out a lot of the uncertainty of reflections, but reduces the time available to take the measurement (with a reflection off a solid surface, you've got about twice the distance - and hence time - to measure). What I was planning on doing was making a ballpark measurement of the ToF (Time of Flight) of the waves through the wort, and filtering out anything that came outside of those bounds (waves through the fermenter wall should arrive much sooner, reflections through the wort should arrive later). Once you establish a reading of the time, you can use that as an estimate of the time the next measurement should take (as the SG of the wort will change very slowly wrt the frequency of measurement). Setting up a band-pass filter on your Rx amplification circuitry works a treat, too.

By using submerged sensors, you take things like krausen out of the equation, assuming that the sensors are sufficiently submerged in the wort. The only problem that I see with MHB's solution, is that a decent load cell (last time I checked) was very expensive. You also don't know how the krausen and top-cropping yeast are going to affect the measurement.

Another approach we thought of was very similar to a refractometer - having a prism built into the side of the fermenter, and using a laser and sensors to make readings. The main problem for us, was one of resolution. We would have needed a very high resolution ($$$) sensor to pick up our laser beam, or a prism of very high refractive index (nothing we could find was high enough - and not opaque). We scrapped this idea, as it is pretty much impossible to do on a budget. The US approach is much more dfficult (and in the end may not even work), but is a much much cheaper option. And of course, as this thread has shown, there are many other options out there, too.

 

[ArgM]

So, the sensor sounds like its more hassle than its worth, probably still gonna by one cause it sounds pretty fun to play with.

Ive got a really rough concept of what I came up with in my musings today about it.
This is kind of what I'm thinking of doing but not savvy with different sensors and how to use them so if someone could help with that it would be appreciated.

So, you have a float gravity reader like the hydrometer with an open end, this is then held and floated in the keg, it is able to move up and down. Into the open end of this hydrometer
is a rod, this road is fixed to the roof of the vessel and cannot move, as the gravity changes the floating vessel will move up and down this rod which through the use of a sensor will be able to
provide a gravity reading once calibrated.

also,

 

[ArgM]

No Rod fans around?