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Old 01-14-2014, 08:56 PM   #1
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Default Level sensing methods

Hi,

I'm in the process of building a electric brewing system. I will be running with an Arduino. I was just wondering what is the best method for measuring water levels. I want to be able to measure and set how much water is pumped from the HLT to the mash tank and so on. But for different recipes this may change so I don't want to just use float switches.
Thanks

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Old 01-14-2014, 10:19 PM   #2
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Install 2 parallel stainless electrodes to your HLT tank (from top to bottom) and measure resistant. Higher water level gives you lesser resistance.

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Old 01-15-2014, 01:14 AM   #3
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Install 2 parallel stainless electrodes to your HLT tank (from top to bottom) and measure resistant. Higher water level gives you lesser resistance.
Does that actually work? I would expect that the "resitance" of the fluid between the electrodes would be many times greater than that of the electrodes themselves - meaning the total resistance of the probes will not vary significantly with differing levels. I have seen this approach do for level switching at a set point but never level sensing for continous level monitoring.
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Old 01-15-2014, 01:42 AM   #4
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Does that actually work? I would expect that the "resistance" of the fluid between the electrodes would be many times greater than that of the electrodes themselves - meaning the total resistance of the probes will not vary significantly with differing levels. I have seen this approach do for level switching at a set point but never level sensing for continuous level monitoring.
The conductivity (inverse of resistance) of the liquid will definitely change much, much more than the height of the liquid. You could probably "calibrate" this gauge by filling it to a known height, taking a measurement, then filling or draining from there. You'd have to do some serious math or do a bunch more tests from there to see how much the resistance drops as you fill. Still, the amount of dissolved solids will have a big effect on the conductivity of the solution so you'd have to adjust your setup every batch - and as you boil off water, the conductivity will change along with the level.

The resistance from two 1-foot sections of stainless rod will be very close to zero in relation to the water/mash/wort in between them. Even "poorly conducting" metals conduct well compared to sugar water.

There are capacitive level probes (typically switches, sometimes continuous transmitters) out there but they're tricky to work with even in industrial settings.

You may be better off with multiple level switches (say, one every gallon or so) and in that case, you could use conductivity. Otherwise, volume is the integration of flow rate over time so you could calibrate your pump (or get a positive displacement pump), or install a flowmeter (a gear type flow meter may not be *that* expensive - haven't tried to price them out for brewing applications).
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Old 01-15-2014, 01:44 AM   #5
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If you are trying to use it for volume measurements. I have seen where people with the Brewtroller use a bubbler somehow to measure volume in the kettle.

A float works well as a safety to prevent the element from firing while the element is exposed. It won't work at telling you the volume of water though.

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Old 01-15-2014, 01:47 AM   #6
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or install a flowmeter (a gear type flow meter may not be *that* expensive - haven't tried to price them out for brewing applications).
I have seen these used for the Kegbot project. I want to say a food safe flow meter was in the $40-60 range. Of course this won't help if there are any leaks in the system and won't tell you what is in the vessel following loss from boiling or general evaporation.
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Old 01-15-2014, 01:54 AM   #7
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Originally Posted by Scotty_g View Post
The conductivity (inverse of resistance) of the liquid will definitely change much, much more than the height of the liquid. You could probably "calibrate" this gauge by filling it to a known height, taking a measurement, then filling or draining from there. You'd have to do some serious math or do a bunch more tests from there to see how much the resistance drops as you fill. Still, the amount of dissolved solids will have a big effect on the conductivity of the solution so you'd have to adjust your setup every batch - and as you boil off water, the conductivity will change along with the level.

The resistance from two 1-foot sections of stainless rod will be very close to zero in relation to the water/mash/wort in between them. Even "poorly conducting" metals conduct well compared to sugar water.

There are capacitive level probes (typically switches, sometimes continuous transmitters) out there but they're tricky to work with even in industrial settings.

You may be better off with multiple level switches (say, one every gallon or so) and in that case, you could use conductivity. Otherwise, volume is the integration of flow rate over time so you could calibrate your pump (or get a positive displacement pump), or install a flowmeter (a gear type flow meter may not be *that* expensive - haven't tried to price them out for brewing applications).
Sorry you may have confused me, are you saying it won't work or it could work. Would the conductivity change depending on the amount of probe in the water?
But as (I think) you are saying theoretically it "would" work but practically it's not going to due to other variable changes that will effect the reading - wort composition, etc.

I have actually bough a cheap turbine flow meter that I am looking to trial to see if I can first measure flows and then if I can calculate volumes from that. I also want to see if I can preform flow control by PWM of my pump.
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Old 01-15-2014, 02:03 AM   #8
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Originally Posted by sennister View Post
If you are trying to use it for volume measurements. I have seen where people with the Brewtroller use a bubbler somehow to measure volume in the kettle.

A float works well as a safety to prevent the element from firing while the element is exposed. It won't work at telling you the volume of water though.
I should really check for myself but...
Is the bubbler type affected by wort density?
Since the bubbler method is actually sensing a pressure and converting that to a level/volume then I would expect it to change. In fact for a 1.050 og beer the error would be just under 5%, for a big beer (1.100+) you would be over 9% error.
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Old 01-15-2014, 02:18 AM   #9
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Sorry you may have confused me, are you saying it won't work or it could work. Would the conductivity change depending on the amount of probe in the water?
But as (I think) you are saying theoretically it "would" work but practically it's not going to due to other variable changes that will effect the reading - wort composition, etc.

I have actually bough a cheap turbine flow meter that I am looking to trial to see if I can first measure flows and then if I can calculate volumes from that. I also want to see if I can preform flow control by PWM of my pump.
I think that what he is saying that it would work but the biggest hurdle would be what is held in solution which could throw off readings. That said if you had a consistent water profile it could work in the HLT. Might not be very usable in other vessels. Too many variables which would impact the conductivity (resistance).
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Old 01-15-2014, 02:20 AM   #10
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Quote:
Originally Posted by mattd2 View Post
I should really check for myself but...
Is the bubbler type affected by wort density?
Since the bubbler method is actually sensing a pressure and converting that to a level/volume then I would expect it to change. In fact for a 1.050 og beer the error would be just under 5%, for a big beer (1.100+) you would be over 9% error.
Honestly I don't know much about it but I do know some people use them here and it is something mainly done over on the Brewtroller side. If you want more info on it take a look at this.

https://www.oscsys.com/projects/brew...me-measurement
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