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Hello, what are peoples thoughts on using a digital hydrometer? I have always wanted to use one myself for the purpose of automation, but was immediately put off by the price of commercially available units. I have seen the Beer Bug out there, which seems like an interesting concept, but a little clunky looking. It is considerably cheaper than commercially available digital hydrometers, but probably has the trade off of lower reliability/robustness, accuracy and perhaps annoying to sanitise. 

I have been developing an ultrasound based density meter (hydrometer) in my spare time for a bit of fun (Electronic engineer by day). The sensor will be a solid state component (no moving parts). Importantly, it would be easy to sanitise and would be robust. The sensor itself would float inside the fermenter, so should have minimal impact on your standard equipment. It would of course be wireless too. 

I am still in the early stages of development, and am at the stage of building a simplified prototype to verify the modelling I have done for the sensor. I am aiming for an accuracy of +- 0.001 SG. If the technology proves successful I may be interested in turning it into a product for home brewers, but the question is what is the max people would pay for a digital hydrometer aimed at home brewers? This would ultimately be the go/no go for further development as a product. I will continue making one for myself regardless. 

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I have an   Atago http://www.atago.net/product/?l=en&f=products_pal.php

Resolution Brix : 0.1%
Temperature : 0.1゚C
Measurement Accuracy Brix : ±0.2 %
Temperature : ±1゚C

I like it and for about the last ten brews have used refract only once and found the measurement accuracy to move around by a lot more then the digital meter (ie refract has low repeatability if multiple measyrements in a row),  I have hydrometer calibrated three times and its been spot on.

They work in low light levels as they have inbuilt led for measurement .  Big plus if you brew a lot at night.

They temp adjust BUT imho if you leave the sample for 2mins then retest you get better accuracy if its 68C wort, instant is fine for just a mash check.   ie your plato can move by +0.5 plato as sample cools from 68C but after 2 mins it settles and repeats every time.

I wouldn't be without it now, but rate my ph pen as actually more important to final beer outcome.

I think there are other industry areas way bigger then home brew, thinking grape growers etc

Interesting unit. How much did that cost you? Pretty reasonable accuracy it has too.

The downside for me is the fact that you still need to take a sample in order to obtain a measurement. I want to create a unit that continuosly outputs data and has the ability to be accessed remotely.

Good point about the grape growers, the wine industry would be another target area.

$225 2nd hand off trademe,  they are about $320 new.

Taking a small sample in most industries is not a barrier, vs hydrometer which requires a lot of sample

I have this device:


It works pretty well and sends values via bluetooth - the downside is you need your phone or a tablet next to it to record.

Using this I have discovered:

a. wort temperature is higher than the fridge cabinet (stc-1000 themoresistor taped to side of fermentor)

b. The first couple of days - gravity really drops fast (I'm oxygenating by wort) - so a diactyl rest is earlier than you think

c. Beers with a high krausen sit on the device, changing the value, rocking the fermentor to get the crap off the top helps.

There is an open source/open hardware version here:





I have seen this unit in my brief search. I don't suppose you have compared the measurements to a calibrated hydrometer by chance? Looks nice and easy to sanitise.

I am assuming you are using a plastic fermentation vessel? The low thermal conductivity of the plastic will give you a little bit of temperature difference. Does the temp difference stay constant between the two devices?

Krausen forming on the top of the sensor shouldnt be too much of an issue for my sensor due to the sensing portion being submersed, so hopefully it will be tolerant in that regard.

Do you have any connection issues with the bluetooth?

I've built one of these: https://github.com/universam1/iSpindel   I've got it doing a calibration run at the moment in my fermenter.   

I picked up parts from aliexpress plus had to get the container tube from ebay.  Putting it together It took a bit of fiddling with a couple of failed builds due to bad circuit layout and borking one of the modules via short circuit...  

interesting - what do you think it cost in parts in the end?

I'd be keen to see it in action - I'm in Auckland.

Sorry for the late response.   Just recovering from Beervana today. :)

Just had a look my ordering history, costs (all $NZ):

  • D1 Wemos $4
  • Charger $2.4
  • Battery $24 (This is brought in NZ)
  • MPU 6050 $1.5
  • Container $4
  • DS18b20 $1
  • Misc. Resistors and switch, board $5
  • 3d Printer PLA $2

So a total of around $44,  the major cost was the battery @ $24.  You could find a cheaper battery somewhere.

The biggest pain was getting a hold of the container,  it was a bit smaller than the open source version but workable but I've now got a couple of spares.

I'm wellington-based I can post a couple of pics in a couple of days.  

Finally finished with it in the fermentation vessel.  Found it a bit difficult to get an 'action shot' so I roped in one of my wife's vases..  



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