Measuring beer left in a keg

I have had interest in finding out how much beer is left in my kegs and have come across some interesting ways.

One can wipe down the keg and wait for the condensation level, or have a temp strip along the edge - wipe down with a warm towel and the beer line will get cooler faster. but this is a manual process.

I have seen a few ways that determine keg use through the use of a flow meter:
KegBot
My Keggerator

The problem I have with this is that my 5 gallon batches are rarely exactly 5 gallons, so you are subtracting ounces as they are used from a set 5 gallon starting point. Now this might be accurate enough, but there is still the issue of waste from foam if the line is foamy (i have this problem when i tap a keg the first time for a lil while). Also, are these difficult to clean?

The way I am strongly considering going about it is by using the weight of the beer. I assume that all 5 gallon corny kegs are going to be about the same weight (so I can zero out to with some degree of accuracy). Here are a few of the potential issues I think I am going to face:
Different beer weighs different amounts
Scales can get expensive when weighing 4 or 6 kegs (I haven't made a keezer yet, and i have decided between 4 and 6 beers on tap at a time)
do i want to hack into bathroom scales (~$20 each) and have a large scale taking up space in the keezer or build my own solution which might cost considerably more than the bathroom scales but be the perfect size to fit under a corny.

Once i figure out which way i want to measure the beer, I have the ability to send the info to the "Cloud" and view it from any internet connected device, but I am looking for some feedback. If you had a perfect way of measuring beer in YOUR cooler, what would it be?

Use your weighing idea, but it will be a bit more manual and won't go into the "cloud", whatever that is.

Weigh the keg when it is empty. Weigh it when it is full. Weigh it periodically after you have tapped it. If Wf = the full keg, if Wr = the remaining beer after a period of time, and if X = the percentage of beer remaining, then (Wf-Wr)/Wf = X. X* V (your starting volume of beer) = how much beer you have.

It likely took me longer to type that answer than it would take to do it.

However, it won't be the amount of beer remaining at a glance that I suspect you are looking for.

You just have to quickly pull the keg out of the keezer to weigh it. Takes about 1 minute.

Thats how I do my CO2. When the weight approaches the empty weight I know a change is coming. I dont worry about my cornies though. I have a general idea of when they are approaching empty.

i am planning on having a scale under each keg whilst it is in the keggerator, so i would have the weight of all kegs at once, not having to pull one out to weigh it, that would be too much like work.

I like the suspense of not knowing which keg is gonna blow first.

Randall said:

I like the suspense of not knowing which keg is gonna blow first.

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I've been engaged in "Keg Roulette" for the last week or so. I was certain I'd have one of the six on tap kick during Turkey Week, but they're all still hanging in there. And even though I have four fresh kegs sitting carbed and chilled, I've trying to keep the game going

As for the idea of using scales, I doubt they'd last for long sitting at the bottom of a cold damp keezer, as condensation would eventually kill 'em...

Cheers!

It's not at-a-glance, but you don't have to pull the kegs out to weigh them this way: Use a fish scale. Mark the tare weight of each keg on the keg. When you want to weigh a keg, hook the fish scale onto the keg handle and lift it up 1". Beer weighs roughly the same as water: 8lbs per gallon. If your keg weighs [tare weight] + 4 lbs, you have about half a gallon left.

Grab the rubber handle on the corny and lift. No faster or simpler way to find out how much beer is left in it.

day_trippr said:

I've been engaged in "Keg Roulette" for the last week or so. I was certain I'd have one of the six on tap kick during Turkey Week, but they're all still hanging in there. And even though I have four fresh kegs sitting carbed and chilled, I've trying to keep the game going

As for the idea of using scales, I doubt they'd last for long sitting at the bottom of a cold damp keezer, as condensation would eventually kill 'em...

Cheers!

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I've had 3 kegs blow in a brew session with maybe 2 pints out of each. Its a good reason to limit the friends pours though " easy, keg is getting low gotta do small pours." That's the only reason why I have any of my Trippel left.

Weight scales are often used in fluid processing. Knowing the specific gravity or density of your fluid is the key # to know the weight /volume ratio.

For example: I know the specific gravity of water is .9979 @ 70 degrees F.

A gallon of water weighs 8.34 pounds.

Even if your beer is slightly heavier (more dense) than water, it is not going to alter the volume enough for you to care about in a 15.5 gallon keg volume. To keep it simple, just use the weight of water.

So, a full keg of beer (minus the weight of the keg) would be approximately 129 pounds. As you start to drink from it you feel the need to know how much is left. You weigh it again and it weighs 89 pounds (once again, not counting the weight of the keg in this example). Divide that by 8.34 and you get 10.7 gallons left in your keg.

You can get much closer if you really feel the need to, but simply using 8.34 will get you close enough without having to measure the specific gravity of every batch and recalculating.

Texan said:

A pound of water weighs 8.34 pounds.

Even if your beer is slightly heavier (more dense) than water, it is not going to alter the volume enough for you to care about in a 15.5 gallon keg volume. To keep it simple, just use the weight of water.

So, a full keg of beer (minus the weight of the keg) would be approximately 129 pounds. As you start to drink from it you feel the need to know how much is left. You weigh it again and it weighs 89 pounds (once again, not counting the weight of the keg in this example). Divide that by 8.34 and you get 10.7 gallons left in your keg.

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that is a heavy pound!

I assume the poster is using cornies and not half barrels but your theory should still work. Welcome to HBT BTW!

Just looked up the weight of a full keg and an empty shell. full keg is about 160 lbs, empty keg shell 29.7 lbs.

Using my calculation , 29.7 lbs (keg shell) + 129 lbs (weight of beer) = 158.7 lbs.

1.3 pounds off, not to shabby.

i was referring to the typo sorry for the bad joke

A pound of water weighs 8.34 pounds.

im sure you meant gallon

On the scale idea you can always DIY a scale, Spark fun (electronic online shop with really cool stuff) has a kegerator that tweets when someone pours and tells everyone how much beer is left.

Here is a link to the tutorial they did on theirs, basically it is a load sensor under the keg (they did the whole fridge as they only run one keg).

Tweeting Kegerator - SparkFun Electronics

I plan on doing this but as I only just got my keg making a decent kegerator is higher priority.

Clem

This $9 idea arrived in 3 days works pretty sweet.



Samsonite Luggage scale.
Empty keg = 7 lbs.
Full 5 gal keg = 46 pounds.
Do the math if you want to mark off individual gallon increments

Tried it and it works great.

They've got more, lots more. Shipment came right from Samsonite:

Samsonite Manual Luggage Scale GREAT PRICE + FAST SHIPPING why go anywhere else? | eBay

Thats 7.8 lbs/Gallon. Does'nt sound right.

Stevo2569 said:

Thats 7.8 lbs/Gallon. Does'nt sound right.

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OK, who stole .3 gallons from my keg..............

I always bottle two or four pints from every batch. That explains it.
What really matters in this thread is when it's getting near empty.

I don't want to know. I am always trying to discover the never ending keg. Just keep pouring and hope it never ends.

i love the link above. i want to put a full time scale under the keg (sanke kegs too) so i could do a quick calculation on how much weight ie how much beer is left. any good scales that are cheap that would get ruined by moisture?

Clementine said:

On the scale idea you can always DIY a scale, Spark fun (electronic online shop with really cool stuff) has a kegerator that tweets when someone pours and tells everyone how much beer is left.

Here is a link to the tutorial they did on theirs, basically it is a load sensor under the keg (they did the whole fridge as they only run one keg).

Tweeting Kegerator - SparkFun Electronics

I plan on doing this but as I only just got my keg making a decent kegerator is higher priority.

Clem

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This is great! Thanks for sharing the link!

I know the thread's a little old, but I found myself here looking for someone who has done exactly this same thing. I picked up a Raspberry Pi - www.raspberrypi.org - and was trying to think of a good use for it. I started to pour a beer (to help with my pondering) when... swooooosh... it was empty. Had I *known* it was going to be empty I would have had another keg cooled and ready to go.

I think the weight route is definetly the way to go. There are USB scales that feed weight data to a computer. The Raspberry Pi runs Linux (and as a bonus, I finally have a reason to learn Linux) and has network connectivity. The plan is to have constant weight - and maybe temp, too - sent to the RP enclosed inside the kegerator with the keg sitting on the scale. The RP will provide the data - converted into "pints left" based on weight - to a web page.

Now to read the whole Sparkfun article someone posted - looks very cool.

MrMatarazzo said:

I know the thread's a little old, but I found myself here looking for someone who has done exactly this same thing. I picked up a Raspberry Pi - www.raspberrypi.org - and was trying to think of a good use for it. I started to pour a beer (to help with my pondering) when... swooooosh... it was empty. Had I *known* it was going to be empty I would have had another keg cooled and ready to go.

I think the weight route is definetly the way to go. There are USB scales that feed weight data to a computer. The Raspberry Pi runs Linux (and as a bonus, I finally have a reason to learn Linux) and has network connectivity. The plan is to have constant weight - and maybe temp, too - sent to the RP enclosed inside the kegerator with the keg sitting on the scale. The RP will provide the data - converted into "pints left" based on weight - to a web page.

Now to read the whole Sparkfun article someone posted - looks very cool.

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i really like the idea of either using an arduino or a raspberry pi to monitor this. going subscribe and see if anyone comes up with anything!

I use this:

http://www.micromatic.com/draft-keg-beer/liquid-management-pid-SS100.html



It works great and is cheap.

What about using http://www.sparkfun.com/products/10245 with an arduino? Get a triangle shaped stand, put one of these under one of the corners, offset the height on the other two, then take the weight given * 3 to get the weight of the keg?
Here's a guide I found real quick http://kegmonitor.webs.com/

If you want to get really creative, an ultrasonic distance sensor mounted inside the keg pointed down can measure liquid level and feed into an arduino.

I wonder how accurate that would be, being inside a metal tube..

Here's another possibility. http://kegbot.org/about/faq/

I would want something rather simple though. What if we used a flow sensor on the auto siphon line as the beer is entering the keg (when you fill it), and then use that total number as a base line for volume. Then we measure the beer flowing out and subtract from the original volume.

If someone could recommend a flow meter that wouldn't disrupt the beer (I have heard there are ultrasonic sensor based meters?) I can get started on this.

I'm thinking about https://www.adafruit.com/products/772 for a display and https://www.adafruit.com/products/828 for the meter

A really old-fashioned way might be to keep a chart next to the fridge. Everytime you pull a pint, make a notation, and keep track of how many pints you have. Of course, you might be disturbed at how much you drink!

at summer parties it is easy,,,, as they get low they start to float in the water and ice...

I just use the grab a lift method nut I would assume the next best thing would be a scale.

At least with a scale you have a device that has multiple uses...

disney7 said:

I use this:

http://www.micromatic.com/draft-keg-beer/liquid-management-pid-SS100.html

It works great and is cheap.

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I do like it, the beauty being its simplicity! But, I'm a sys-admin and all 'round computer geek with a Raspberry Pi I need to justify purchasing

brewn00b4 said:

Here's another possibility. http://kegbot.org/about/faq/

I would want something rather simple though. What if we used a flow sensor on the auto siphon line as the beer is entering the keg (when you fill it), and then use that total number as a base line for volume. Then we measure the beer flowing out and subtract from the original volume.

If someone could recommend a flow meter that wouldn't disrupt the beer (I have heard there are ultrasonic sensor based meters?) I can get started on this.

I'm thinking about https://www.adafruit.com/products/772 for a display and https://www.adafruit.com/products/828 for the meter

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SOLD! I just ordered the kegboard, coaster and full parts list (minus the RFID reader). I wish they had mentioned what flow meter they are using, the ones I'm finding are >$200! Let me know if you find one thats inexpensive. I'm going to try using the Raspberry Pi instead of the Adruno, though. I'll keep you guys updated on how it goes.

MrMatarazzo said:

... I wish they had mentioned what flow meter they are using, the ones I'm finding are >$200! ...

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Someone posted a complete parts list (including $60 flow meter) in their forums.
http://kegbot.org/kegbb/topic/186/

MrMatarazzo said:

...I'm going to try using the Raspberry Pi instead of the Adruno, though....

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I'm not aware of any way to currently use an arduino shield on a raspberry pi, so you may be stuck with that platform for now (if you want to use the kegbot shield). I would keep an eye on Ponte, though. It looks like it might do what you want.

that is a pricey flow meter, I thought I found one <$20. Let me see what I can find.

here it is http://www.seeedstudio.com/depot/g1...=84_87&zenid=0dfaf037192e49ad17ec3398429fdff2

lorglath said:

that is a pricey flow meter, I thought I found one <$20. Let me see what I can find.

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It all depends on the level of accuracy you're looking for.

lorglath said:

here it is http://www.seeedstudio.com/depot/g1...=84_87&zenid=0dfaf037192e49ad17ec3398429fdff2

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Just a warning that these are not "food safe". I developed the MyKegerator.net system and this is the major issue we are having in producing something for sale. It is hard to find flow meters that are FDA/NSF rated, durable, and cost-effective.

The Swissflows are food safe, however are expensive.

Have fun!

e12pilot said:

Just a warning that these are not "food safe". I developed the MyKegerator.net system and this is the major issue we are having in producing something for sale. It is hard to find flow meters that are FDA/NSF rated, durable, and cost-effective.

The Swissflows are food safe, however are expensive.

Have fun!

Click to expand...

While not necessarily "food safe", it does appear the components are safe. http://www.seeedstudio.com/wiki/index.php?title=G1/2_Water_Flow_sensor#FAQ