Low flow rate accuracy

[treiff]

@CapnBry, This is great. Thanks for putting it together. I'm thinking about building two of these to assist in matching my sparge water into the mash tun to wort out into the boil kettle.

Just curious if your thought the accuracy was acceptable at low flow rates or aprox: 0.5 l/min. I assume you just calibrate to the flow rate you expect to use most often?

Thanks.

[CapnBry]

Hi Trevor, The only measurement device I have used it with is the Adafruit 1/2" which is rated 1lpm - 30lpm. Its accuracy below 1L and even around the 1L mark is pretty abysmal as the impeller starts to stall out or rotate on its own. Still, I'd say the error rate is below 5% on the low end there. I also have purchased a smaller device from eBay which is rated 0.3L to 6L which would probably be better suited for these rates, but I couldn't get a good leak-proof connection because my setup has heavy 1/2" tubing with big stainless quick disconnects so it applies enough force that it bends the tubing going into the sensor and it leaks pretty badly.

However, if your design uses more lightweight tubing and/or has a way to hold everything down it should work. You'd just need to change SENSOR_HZ_PER_LPM and recalibrate the constants in the SCALE_LEVELS[] table at the top. You can just have one entry in the SCALE_LEVELS table to start, with just {0, 1.0f} which will remove the variable scaling altogether.

[treiff]

Okay, great. Yeah, I've got a setup similar to kal's at the electric brewery. I might be in a similar situation as i've got the 1/2" silicone hose with SS disconnects.

I think I can figure a way to hold everything down, I'm not to worried about it being super accurate. It's worth a shot, I haven't done much with the arduino so should be a fun little experiment.

[CapnBry]

Another electric brewery! I still use the Flowknow every brew day. It is good for getting a good ballpark figure. Like during mash I set it to 1 GPM, which is what the Blichmann 15 gallon false bottom is rated for and then shut off the flowknow. At sparge time I set for 0.75lpm for a 5 gallon batch or 1lpm for a 10 gallon batch and then adjust the flow rate on the sparge water to match using the "binder clip on the sight glass" method.

Flowknow works perfectly well for that, but the number bounces around +/-10% at those low flows and the total volume at the end is off by 10% (usually indicating more if I remember correctly, but since I put a sight glass on the boil kettle I have stopped looking at the total). If you do build something with the smaller sensor I'd love to see it. Also feel free to contact me directly at my email address, which is my username here at gmail.

[treiff]

Thanks Bryan, I'm planning on putting something together in the near future. I might pick up a smaller sensor just for fun. Anyway, thanks for your input. If I have any questions I might ping you via email if that's cool. Thanks again!