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Old 02-09-2013, 05:58 AM   #31
craigmw
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Originally Posted by MalFet View Post
Those are new prices, though. Second hand units are readily available on ebay for sub-$60. The various gas-specifications are just a matter of a coefficient. There's a simple multiplier to convert between units.

I guess I'd like to go with an approach that I could publish here, and using an off the shelf part that others could use would make this work better. I just need to figure out how to convert this particular part for EtOH instead of air.

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Originally Posted by MalFet View Post
Sure, it sounds like a great approach in theory. Have you found a sensor that operates in a range useful for homebrewers? I'd like to give it a whirl to see if it actually works experimentally, but the sensor you linked to won't work.
A couple of thoughts here... there are IR based ethanol sensors that use an IR spectroscopy approach with a spectral peak around 2900 nm indicating ethanol. I'm still trying to find a cheap solution for this. An alternative is to use ethanol sensors for E85 gas. These are flex fuel vehicle sensors that can detect the level of ethanol in gas between 0 and 100%, and send a frequency output based on this. I'm not sure this would be sensitive enough for beer though. So the issue is that the MQ3/MQ303 chip based EtOH sensors are too sensitive and the auto flex fuel sensors may not be sensitive enough for the typical 3-8% EtOH levels we usually see in finished fermentations. I think the best approach is the IR spectroscopy method, but I'm yet to find a reasonably economical solution for this.

 
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Old 02-09-2013, 06:15 AM   #32
alien
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You'll never be able to calibrate those electronic ethanol sensors accurately enough. They usually require 24 hours of preheating too.

 
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Old 02-09-2013, 01:11 PM   #33
MalFet
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Quote:
Originally Posted by craigmw View Post
I guess I'd like to go with an approach that I could publish here, and using an off the shelf part that others could use would make this work better. I just need to figure out how to convert this particular part for EtOH instead of air.
Great! Let us know if you get something working.
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Old 02-09-2013, 04:26 PM   #34
alien
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Malfet, would this kind of flow meter be completely useless?

http://www.coleparmer.com/Product/Gr...gs/EW-32206-04

Need something with an electronic readout I reckon.

 
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Old 03-07-2014, 05:18 PM   #35
newtonjason
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Hey Everyone, just saw this thread and although its a year old now, I figured I'd chime in.

I use a bubbler liquid level sensing system in my apartment setup using an arduino to read the voltages from an MPX5010dp differential pressure sensor (0-3ft of height is 0-5V). This works well as you have one port reading the pressure of the height of liquid, the second is open to atmosphere for reference.



I'll be using this technique to do automated gravity readings with two bubbler tubes spaced a few inches vertically apart from eachother. I'll feed the system initially with an aquarium air pump however may eventually use C02 (from either a bottle or a C02 bath created by the fermentation of the beer itself The bubbling of the system as previously mentioned is not really an issue as you can filter this out with software.

Reasons I will be using the bubbler are:
1. no concern over crud or krausen or any other debris accumulating on the tubes
2. Already use a single bubbler tube for liquid height measurement on my brewery so integrating this will be simple
3. Its very simple (not as simple as an optical sensor in the airlock) and its output directly measures gravity not back calculating it from bubbles or mass flow of C02 or weight etc.....

I'm sure I'll learn a thing or two while doing this project so I'll be sure to keep everyone up to date with how I am progressing on this.

As this is a learning forum, please challenge anything i've said above if it doesn't seem to add up

-Jason
www.brewbot.ca

 
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Old 03-10-2014, 07:34 AM   #36
tob77
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I hate to be a naysayer, and I think bubblers are great for volume measurements. However, I think that you should do some preliminary calcs before you go too far down this road. I don't think that you will be able to get the resolution that you are looking for. Even if you place the differential bubblers a foot apart the pressure change with respect to SG will be very small. I think that it would be something like 0.00043 psi per gravity point.

 
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Old 03-10-2014, 06:27 PM   #37
Oyvindt
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Time to come out from lurking mode I suppose! I did an experiment a while back using a differential pressure sensor:

http://www.digikey.com/product-detai...660-ND/2704715

.. and a couple of tubes going in to a very ad-hoc-and-experimental fermentor vessel:




This is the result:



The wort OG was 1.043, and it ended at 1.018 (it was fermented in a too cold basement with too little WLP400, which is probably why it stopped early. No oxygen added or shaking wort either..) The values on the graph is voltage * 1000 so there is a 300 mV difference from start to finish.

 
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Old 03-10-2014, 06:51 PM   #38
markstache
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How about calibrated weights (e.g. BrewBalls) with RFIDs inserted in them? Have a RFID reader at the bottom of the tank that reads which balls have fallen.

 
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Old 03-12-2014, 03:04 AM   #39
mattd2
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Quote:
Originally Posted by Oyvindt View Post
Time to come out from lurking mode I suppose! I did an experiment a while back using a differential pressure sensor:

http://www.digikey.com/product-detai...660-ND/2704715

...This is the result:



The wort OG was 1.043, and it ended at 1.018 (it was fermented in a too cold basement with too little WLP400, which is probably why it stopped early. No oxygen added or shaking wort either..) The values on the graph is voltage * 1000 so there is a 300 mV difference from start to finish.
Nice work, the graph looks promising that you can use a DP to measure SG changes - would a cheaper sensor work like http://www.digikey.com/product-detai...1TR-ND/1168437 looks to have similar scale and accuracy values???
I was going to suggest making the carboy/bucket into a capacitor with 2 sheets of copper wrapped halfway round each and measure the change in capacitance

 
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Old 03-12-2014, 08:58 AM   #40
Oyvindt
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Originally Posted by mattd2 View Post
Nice work, the graph looks promising that you can use a DP to measure SG changes - would a cheaper sensor work like http://www.digikey.com/product-detai...1TR-ND/1168437 looks to have similar scale and accuracy values???
That seems like a suitable replacement I have no idea why I picked the specific sensor that I used. It was probably just the first one I found that had suitable specs..

 
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