Flow Sensors for beer tap monitor

Since I'm getting a keg soon, I think it would be fun to meter how much we've poured. This was discussed a little in Arduino based monitor system. Below is a list of the sensors people listed in the the Arduino monitor, and one I found. I wanted to start with the sensor, then decide on the rest of the system.

So, lets start with the questions -
How how fast is a typical pour? Not having a keg yet, I have no idea.
Which sensor did you use?
How well does it work?
Any specific reason you bought the one you did?
Other Suggestions?


http://www.seeedstudio.com/depot/g1...=84_87&zenid=020999c566d2f31841dc54602b7d02ef
Flow Rate: 1-30L/Min, up to 3% accuracy 1-10L/Min, $9.50
not for strong acids or bases, ok for drinking water

http://www.swissflow.com/sf800.html
Flow Rate: .5-20 L/Min, +/-1% accuracy, $60 +$20 shipping
States good for beer, used in Kegbot.org

https://www.adafruit.com/products/828 Plastic, $10
https://www.adafruit.com/products/833 Brass, $25, ROHS Compliant
Flow Rate: 1-30 L/Min, "needs calibration for better than 10% accuracy...", $5 shipping

Another I found -
http://www.futurlec.com/Flow_Sensor.shtml
1.5-14.1 L/Min (3/8in Pipe), 10% Accuracy, $9 + $4 shipping
Made for Water systems

If you just want to see how much has been poured, I would measure by weight like these guys.
http://www.sparkfun.com/tutorials/144

The only question I have an answer to is the pour rate. The Draft Beer Quality manual say it takes something like 8 seconds. You can look it on in that publication.

I agree that weight of the keg is likely the best way we have of monitoring how much beer has been poured, and how much remains. If you do go with measuring the time the tap has been open, you'll need to be extremely careful about maintaining the same pressure on your co2 regulator, keeping in mind that it will change with temperature.

As for the in-line flow sensors you listed, those would be pretty cool to play with. Just keep in mind that carbonated beer is acidic, and a few of them are only for water.

The line balancing equations and calculators all assume a flow of 1 gal/min (3.79 L/min). If you ever want to serve beer warmer than 38° or at a higher carb level like a lot of us, you'll probably want longer lines to prevent foaming, which will slow the flow down some.

You want to measure the flow for the fun of it? I don't get that. I could understand wanting to know how much is left in the keg. A scale would work well for that. Since you can easily measure the specific gravity of the beer with a hydrometer you can pretty quickly convert the weight into ounces.

I'm picturing an odometer on your dispenser. That sounds fantastic. Useful? No, but imagine how much you will drink when you see 100, and 1000 (dare I say 10,000? I wont judge) pints roll around on that bad boy! That's like an extra new years, just for drinking more beer!

Make it work!

I'm an Electrical Engineer. The more dials and buttons, the better (although SWMBO disagrees)

One of the other posts I read talked about using a force gauge and calculate the weight, which would make you change settings per beer due to the specific gravity, although with the 10% accuracy of some of the flow sensors, I can only assume the error would be near equivalent.

The only one I've found that actually used force sensors is Sparkfun. http://www.sparkfun.com/tutorials/144. They used 4-100lb sensors (for one keg?). I think it would be easier to build, and to expand in the future with a flow meter.

I'm thinking about ordering the brass one. But I also read that certain metals cause off flavors (hence all stainless in commercial applications...) Thoughts?

BrothOfVigor said:

I'm picturing an odometer on your dispenser.

Click to expand...

For starters, I was thinking about one of the old-school needle gauges (similar to this) that I have in my junk box. Swap out the numbers to be like a gas gauge, Full to Empty. And also have it sense when the tap is open and switch to show when your pint glass is full.

BrewingReverend said:

...I would measure by weight like these guys.
http://www.sparkfun.com/tutorials/144

Click to expand...

fall-line said:

I agree that weight of the keg is likely the best way...

Click to expand...

mrstevenund said:

...One of the other posts I read talked about using a force gauge and calculate the weight, which would make you change settings per beer due to the specific gravity, although with the 10% accuracy of some of the flow sensors, I can only assume the error would be near equivalent.

The only one I've found that actually used force sensors is Sparkfun. http://www.sparkfun.com/tutorials/144. ...

Click to expand...

Beware that most of these sensors are not made to measure under a constant load. The longer you have weight applied - the more your reading drifts off. Another issue can be temperature drift, though that can usually be solved electronically (Wheatstone bridge)

If someone comes up with a truly good implementation for accurately monitoring the weight of a keg, I'll owe them a homebrew. In my kegerator build, I've been mulling over this question for some time.