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Old 12-14-2012, 03:18 AM   #11
Vesku
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Yes it can, that's what I'm planning to do. And then use that info with the Arduino. Try "Wheatstone bridge" in the Google.

 
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Old 12-14-2012, 04:58 AM   #12
matho
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I use load cells out of a cheap electronic bathroom scales and use a single supply instumentation amp



R3 thru to R6 represents the load cells, I have adjusted the gain to give me 5v at 102.3 kg which gives me 100mL resolution on a 10 bit ADC. I have been using it on my HLT for a couple of years now and has worked well, my theory is that if you know how much water you put in you will be able to work out how much you will get out because losses are fairly static.

cheers steve

 
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Old 12-14-2012, 02:51 PM   #13
ryan_george
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I guess all of these load measurements are only good if you're dealing with straight water? Or if you know the SG of your wort....

 
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Old 12-14-2012, 03:06 PM   #14
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Best way is to submerse 2 parallel electrodes in there and measure the resistance (conductivity) between them. The electrodes could be sank into the kettle, or in a sight-gauge-like assembly outside the main volume.

The electronics to monitor doesn't need to be complex; a simple voltage divider would work.

Since the resistivity of the wort will change with recipe, etc, another pair could be used to normalize the depth measurement. This pair would be small, i.e., 1/4", and would provide a constant resistance value. This pair goes to the bottom of the tank and is wetted as soon as wort is introduced.

Use the ratio of the two electrode pairs to determine depth in any conductive fluid.
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Old 12-14-2012, 03:15 PM   #15
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That seams like the most straight forward way of doing things but the electronics are way above my head.

 
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Old 12-15-2012, 03:52 PM   #16
MrNatural
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Quote:
Originally Posted by Vesku View Post
Yes it can, that's what I'm planning to do. And then use that info with the Arduino. Try "Wheatstone bridge" in the Google.
Wow, damn near ancient technology

Quote:
Originally Posted by passedpawn View Post
Best way is to submerse 2 parallel electrodes in there and measure the resistance (conductivity) between them. The electrodes could be sank into the kettle, or in a sight-gauge-like assembly outside the main volume.

The electronics to monitor doesn't need to be complex; a simple voltage divider would work.

Since the resistivity of the wort will change with recipe, etc, another pair could be used to normalize the depth measurement. This pair would be small, i.e., 1/4", and would provide a constant resistance value. This pair goes to the bottom of the tank and is wetted as soon as wort is introduced.

Use the ratio of the two electrode pairs to determine depth in any conductive fluid.
I think I like this approach.

You could set the default resistance to the range of thermistors used by PIDs and calibrate/display the results as volume instead of temperature?

Are there modules/boards or any off-the-shelf solutions to bridge between electrodes and PID?

Guessing the electrodes would need to have some sort of native resistance for there to be an easily measurable change as level of submergence varies?

I'm wondering how much the linearity would be affected by differences in the conductivity of the fluid? Would it be tough to calibrate each use, especially as the chemistry of the wort changes during the mash, and whatever effect that has on conductivity?

Appreciate the input.

Dale
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Old 12-15-2012, 04:42 PM   #17
MrNatural
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Quote:
Originally Posted by matho View Post
I use load cells out of a cheap electronic bathroom scales and use a single supply instumentation amp



R3 thru to R6 represents the load cells, I have adjusted the gain to give me 5v at 102.3 kg which gives me 100mL resolution on a 10 bit ADC. I have been using it on my HLT for a couple of years now and has worked well, my theory is that if you know how much water you put in you will be able to work out how much you will get out because losses are fairly static.

cheers steve
Interesting. Do you have any pics of the physical setup? What is max load for the load cells?

Dale
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Old 12-15-2012, 05:12 PM   #18
passedpawn
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Quote:
Originally Posted by MrNatural View Post
Wow, damn near ancient technology


I think I like this approach.

You could set the default resistance to the range of thermistors used by PIDs and calibrate/display the results as volume instead of temperature?

Are there modules/boards or any off-the-shelf solutions to bridge between electrodes and PID?

Guessing the electrodes would need to have some sort of native resistance for there to be an easily measurable change as level of submergence varies?

I'm wondering how much the linearity would be affected by differences in the conductivity of the fluid? Would it be tough to calibrate each use, especially as the chemistry of the wort changes during the mash, and whatever effect that has on conductivity?

Appreciate the input.

Dale
It would be linear as long as the two rods were spaced evenly apart.

The second set of electrodes automatically calibrates to the conductivity of the fluid, so it's not a factor. That's why the ouput from this is a ration of Electrodes1 / Electrodes 2, where Electrodes 2 are small and the depth of the fluid doesn't affect them.

 
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Old 12-15-2012, 10:04 PM   #19
Vesku
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Quote:
Originally Posted by MrNatural View Post
Interesting. Do you have any pics of the physical setup? What is max load for the load cells?

Dale
Do you see, there's that "Wheatstone Bridge" right there

Have anyone tried to build the 2 electrode system? I've seen some discussions about it, but they all measured capacitance rather than impedance. There was issues with heat affecting the readings. Also an AC current is needed for the measurement to avoid electrolytic corrosion.

If only a few different level indication are needed, here's a simple circuit that works: http://www.electronic-circuits-diagr...msimages/6.gif I didn't have LED's on mine, but send the info to the Arduino. I also had 3 CD4066's get more levels.

 
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Old 12-17-2012, 07:13 AM   #20
Chowhound
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If you just want on off control you could rig up some type of magnetic float in your sight glass that would pick up a read switch mounted on the outside of the sight glass, just slide the switch up and down the sight glass to set your level. You could have multiple switches for different levels, hi, low, hi-hi, low-low.

 
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