Wow, very cool. I'm thinking of what kinds of vessels could be easily adapted to a DIY version of the sort of spring-loaded bubble making frame in the Mini Buck. Maybe like two nested cylinders , with a spring between... hang on, i'll doodle it.

OK, what about a pair of electric wires at the top which are connected by the bubble membrane before it's popped? And a rubber band based harness for dipping?

@warren How do you start the timer? I don't see a sensor for the start, only the end. Another set of electrodes appear necessary. Will that set of electrodes pop the bubble?

A bubble will have to be formed before air flow starts or you will blow bubbles thru the bubble juice which perhaps will be bad.. Unless the cylinder is kept very still (vertically) the bubble will not represent an accurate volume measurement.

This configuration only works for blow and not suck. An attachment for the tube would need to be fixed to the top where the hose would have to kept still during the measurement.

I like the bubble management of the Buck. Only a small rod to seal and the flow does not have to be interrupted to start a bubble. Your gasket may have a problem with leaks

Can you add salt to a bubble solution to make it more conductive and still have good bubble forming characteristics? Is it conductive enough (what ever that means) without adding salt?

The cylinder volume can be calibrated with water and a sensitive balance or accurate graduated cylinder.

Yeah Dan, I later realized that a draw valve at the top would be better than a push valve at the bottom, and I think it'd mean the gasket would be unnecessary.

@mathew Great work and the title is appropriate! Sometimes when I’d compare instruments head to head it would be referred to a “shoot out”—an instrument dual of sorts.

A few observations:

1. I’d like to see multiple Buck tests per test flow rate—at least three to show how precise the Buck performs but take more since it's so easy to use. Any bubble meter, whether it’s a DIY cylinder or a commercial timed system, is prone to errant readings caused by oddly shaped bubbles.

2. The last tube 2 cylinder time of 39.78 seconds looks like an error and could be transposed incorrectly from your notes since it’s the exact same time as the first time for tube 3.

3. This analysis quickly becomes a question of “how close is close enough?” I wouldn’t assume the Buck is perfect and all the flaws are that of the cylinder method. Looking at Buck’s specifications for this model the flow ranges from 0.1 to 30 lpm with +/- 0.5% of reading accuracy. That is a huge range and extremely small error. I’m skeptical the Buck performs this well at the extreme low end of 300 ml per minute. Manufacturers often exaggerate their performance specifications.

I think the cylinder method could marginally be improved with a glass apparatus but you'd probably need to buy this type of glassware rather than make your own. I'm not sure how much it would improve the timed cylinder method but glass is easier to read, typically has finer markings, and the volumes are often more reliable if made by a reputable brand.

Looking at your data--and omitting the 39.78 time for tube 2—the DIY cylinder seems to be well within 1% precision—it’s very consistent.

Here's how I graphed the results, with the one time I question circled in red.

@DavidMack Good catch! My notebook measures test 2 at 38.78, right next to 39.78 for the next test! I edited the note. thanks!

You're right about the Buck not being perfect-- sometimes it gets bubbles in the cylinder and gives a good bit of trouble-- a "side bubble" will form on the film traveling up the cylinder and drag the film sideways. All my MiniBuck tests for this research note were in triplicate-- the only variaion I had was in test #2 where it reported 312 twice and 313 once.

I agree a glass apparatus would be better-- I worry about compressing or messing up the plastic. The problem is the price! A 1000ml Burette is used to calibrate the Mini-Buck, and its more than $200 with shipping! I did some tests with a $45, 50ml pyrex pipette-- the biggest I could buy in-town-- but the bubbles just travel too fast in that apparatus.