Low cost flowmeter

MortenB

Member
Join Date
Apr 2016
Location
Fredrikstad
Posts
16
Hi everyone

I'm in the process of automating my home brewery. To get control of levels i was thinking of measuring the flow of water into the system. Can anyone reccommend a low cost flow meter? Prefer 4-20mA or 0-10V output.

I have been looking into using load cells but could not come up with a good low cost design for placing the load-cell(s). The system is built up with 3x100l kettles standing on a table.

//morten
 
Flow is not the ideal tool for measuring levels. It will only give you change of level. If it needs to be cheap the measurement of change will not be very exact, so you'd get approximate results at best.

If you need to fill an empty container to a known level from a constant pressure source (water service pipe), the amount you get is directly proportional to how long you open a valve, so it could be as simple as solenoid valves controlled by timers. It will be pretty straight forward to calculate valve open time from the desired quantity with a few tuning runs.

Filling one container from another is different: the flow will not be constant as a higher level in the source container = higher flow. In that case a timer will not give good control over the quantity.

The first thing I thought of was load cells: having a weight at the start and end seems to me the most effective way of controlling the amount you add. What is the issue with load cells? Is it construction (mechanical) or electric/logical (amplifier, AD conversion)?
 
a simple watermeter could do the trick, there is always a red dot, and you can use a photocell to see the pulses.
However this only for water coming in.
Y ou have to think about contamination if used with any other step in process.
cheap ones are available on the arduino platform.
 
The first thing I thought of was load cells: having a weight at the start and end seems to me the most effective way of controlling the amount you add. What is the issue with load cells? Is it construction (mechanical) or electric/logical (amplifier, AD conversion)?
The issue is indeed construction. I could not find a good way to mount a load cell (I have two, both S-beam and a beam cell. I agree that load cell is a good way to go but I'm struggeling with coming up with a good construction.

//morten
 
The issue is indeed construction. I could not find a good way to mount a load cell (I have two, both S-beam and a beam cell. I agree that load cell is a good way to go but I'm struggeling with coming up with a good construction.

//morten


Fluids by their very nature distribute evenly across a horizontal plane. Therefore a fluid container can be mounted on three points in a triangular layout, where two are hinged points and the third point rests on one load cell. With a flat bottom container the very last bit of fluid can give some deviation in your measurements since that last bit of fluid will probably tend to be a tad off to one side. Other than that you should be fine.

One thing to keep in mind in your construction is to make sure the container can move freely with nothing touching from any side other than the three mounting points. It will move a fraction of a milimeter when being charged, moving back up when unloading. Your readings will be unreliable when things are leaning against or on it that inhibit these micro movements.

Does that help?


Addition:
Check your S beam cells for their properties - are they made for tension, compression, or both. Some are made for tension only, which means you have to "hang" your container (tension of the weight pulls the s-beam apart). If compression only, the construction on the other hand should be such that the weight rests on the load cell (compresses it).
 
Last edited:
Not sure what your budget is, but if you are looking for level measurement this may work for you.

Flowline Echopod is about 280 from automation direct for a 0-10v sensor
 

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