Brewtroller bubbler

[Mpavlik22]

Can anyone explain this further? I read this but still don't understand the concept or reasoning behind its need/function.
Thanks

 

[Tinga]

my complete shot in the dark is that it uses the amount of pressure provided by the level of liquid in the vessel to measure the amount of pressure needed to bubble. this pressure is measured by the sensors to read out a digital volume or liquid in the vessel. take this with a grain of salt because it is a complete guess.

 

[LandoLincoln]

Sounds like a really convoluted sight glass.

 

[hot_carl]

I think Tinga is right...it looks like the sensors would be sensing backpressure in the lines which would vary with liquid level. When the level was higher, it would take more pressure to force bubbles out of the line. These pressure readouts would be cross referenced with pressure readouts of known liquid volumes, or calculated by whatever brew program they are using to give an actual liquid volume as a readout. I'm not sure how well this would work once you introduce boiling into the equation since vater vapor in the boiling bubbles is a different pressure than the surrounding liquid.

 

[mattreba]

The sensor measures the amount of pressure caused by the height of the liquid in the vessel. There is air in the line as the sensor does not directly contact the liquid. When the temperature increases the excess air bubbles out but the reading is still accurate. However when the temperature falls a vacuum is formed and the reading will be off. By feeding a small amount of air we can eliminate this issue. Excess air still bubbles out and we never have a vacuum.

 

[crush]

Sorry to revive an old thread, but the BT site is unpredictable at the minute (can't find any of the old forum posts on the bubbler.)

I would like one of these in my boil kettle. I understand how the bubbler works, but I can't see how a single pressure reading can tell you the volume accurately unless you factor in the gravity of the wort. For water, it's fine since the gravity is as good as constant. For the boil kettle, I can only see that we need two bubblers at different depths, and the known difference in volume between them can then be used to compute SG.

I hope someone confirm this or show where I'm going wrong. Thanks!

 

[BrotherGrim]

Crush, I don't think you are wrong, but the changes in SG are so small from a pressure differential standpoint, I don't think it will have much of an impact. A 1.1 gravity will put you off by 10% in level. Volume can only be calculated by the diameter of the kettle. The DP cell will only give you level above the penetration in the tank.

 

[emjay]

For the boil kettle, I can only see that we need two bubblers at different depths, and the known difference in volume between them can then be used to compute SG.

I'm not sure if you're saying this is how it works, or if that's how it SHOULD work? Because volume can certainly be computed with this method (assuming kettle diameter is also known).

 

[emjay]

Crush, I don't think you are wrong, but the changes in SG are so small from a pressure differential standpoint, I don't think it will have much of an impact. A 1.1 gravity will put you off by 10% in level. Volume can only be calculated by the diameter of the kettle. The DP cell will only give you level above the penetration in the tank.

Even 5% of volume is significant. If I went to the trouble and expense of doing this, I'd certainly expect accuracy to be within a couple percentage points, hopefully less than 1%.

 

[BrotherGrim]

Yeah, I tend to agree with you about wanting accuracy for this complex a system. I didn't say that I was a proponent, just making an observation about the inherent accuracy. As the temperature changes the SG changes anyway, so I fail to see how this could be that accurate.

 

[emjay]

Yeah, I tend to agree with you about wanting accuracy for this complex a system. I didn't say that I was a proponent, just making an observation about the inherent accuracy. As the temperature changes the SG changes anyway, so I fail to see how this could be that accurate.

If there are sensors at two levels a known distance apart, temperature would be irrelevant. If it was temperature-related, the pressure delta would react appropriately due to the accompanying increase or decrease of the wort column (due to thermal expansion/contraction).

As long as you know what the boiling (or whenever) SG needs to be to achieve a desired room-temp SG, which is very easy, the number is just as useful. I suspect the biggest potential accuracy problem would be in the human measurement of the "known distance", or the (also human) placement of the sensors at said distance. Which shouldn't even be that significant unless said human *really* messes up.

 

[crush]

Great, this is what I was thinking. To avoid the human error in placing the two bubblers at a distance, I would not try to measure the distance at all or the diameter of the kettle, but instead calibrate by filling with a known volume of water. I can then calibrate the difference in pressure from both sensors against the known volume and sg.

 

[emjay]

Great, this is what I was thinking. To avoid the human error in placing the two bubblers at a distance, I would not try to measure the distance at all or the diameter of the kettle, but instead calibrate by filling with a known volume of water. I can then calibrate the difference in pressure from both sensors against the known volume and sg.

That'll work. You'll be best off using a beaker (or other laboratory glassware) for filling to the known volume though, as many consumer items are off by a rather surprising degree.

 

[Dan]

Can anyone explain this further? I read this but still don't understand the concept or reasoning behind its need/function.
Thanks

No idea why a homebrewer would ever need this. It's function is add auto pilot to home-brewing and degrade our intellect.

 

[crush]

Just to give another perspective, I need it since I have poor eyesight. I have blichmann kettles, and the laser etched markings are difficult to read. I always find it a strain to read the volume. Also, I will be gradually building in more automation, and digital volume sense is a key part of that.

 

[crush]

for calibrating, I was thinking of weighing the water. I have some digital scales which I think are accurate, and certainly more accurate than I can read a scale on the side of a conical flask.

Although if there is some error, the absolute volume does not need to be so accurate. I'm more after consistent readings and being able to read small changes in volume.

 

[kladue]

There are formulas to correct for the density as temperature changes, and a simple time/evaporation formula to correct SG as the boil progresses. Whether these can be implemented in the brewtroller is the question. There are some media isolated integrated sensors from Freescale that would eliminate the need for a bubbler, look for integrated versions with 1-1.45 PSI - or 6 -10Kpa span. Mounted in cool area and tubed to port on base of keg/pot, will give pressure reading that is ideal for use with brewtroller.

 

[crush]

Thanks for the tip on the sensors and calculating SG based on boiloff. As it is, I've already got the MPX5010DP sensors so I'll be trying to use those. I'd also prefer to measure the SG rather than estimate it. Anything that can be done digitally will save my having to strain to accurately read a hydrometer or refractometer. I'll put two bubblers side by side, of different lengths and try to calculate the SG and volume from that.

 

[kladue]

Save the effort with dual sensors, no one in industry has been able to make that work, sensors are just not accurate enough for that, or else we would see SG calulating devices based on differential pressure. It would be easier to just do a calc based on water volume, Lbs malt, efficiency to get to approximate SG value pre boil, then adjust for volume decrease as water evaporates.
I have done this and other calculations for use with automation application for measuring volumes in mash and boil kettles where density was calculated based on what was in kettle and the temperature.