UPDATE: a newer BeerBug unit seems to have resolved these problems – see Another BeerBug, Another Review.
SECOND UPDATE: Further test results reported here
To follow up my first impressions, here are my experiences after using the BeerBug hydrometer to measure the gravity of a batch of beer as it brewed. As one of the first recipients of the device, I understood that there might be some snags, and so far the people at BeerBug have been very responsive in answering questions and the like. For example, several of the issues I had were resolved by new Windows software. Despite this, I found that my BeerBug is not (yet) usable for its intended purpose of measuring gravity during fermentation.
The beer I’d planned was a weizen. After letting the torpedo stabilize in water for a couple of hours while I finished the brew, I put it in the wort which was intentionally under-pitched. The first few hours showed what seemed to be a vigorous fermentation with a quick drop in gravity, but there was actually no airlock activity.
This was my first encounter with a wicked tendency of the BeerBug to drift. Shortly after this, the battery died: turns out the BeerBug has a built-in memory so it’s better to leave it disconnected from the Bluetooth connection to the PC which will spare the battery and also allow the on-board software to average the collected data (over a user-selected period of time, recommended as 10 minutes) while discarding any odd outlying points. The data was also preserved while swapping the battery.
With the new battery the BeerBug seemed to work OK for a few days. The weather was such that the air temperature in the basement varied considerably between day and night, but the beer in the 10 gallon fermenter held a relatively stable temperature. There’s not yet an immersed thermometer and as a result, it seemed that the temperature compensation of the BeerBug over-corrected in calculating the specific gravity, as seen in the beginning of the below data with diurnal swings.
The chart immediately above begins at a time near the end of fermentation with the BeerBug SG matching closely with that determined by a conventional hydrometer. But a downward drift began that had the SG at times below 1.000, well below the actual beer which finished at 1.011. Then the depicted gravity started drifting upward substantially.
Around the time the above chart ends, I bottled the beer and put the BeerBug in water to see what it would read.
Then things got really weird:
The BeerBug went from the fermenting beer into water at around the time of the big spikes in the above chart. The upward drift continued and then some really strange oscillations began as well. I have no idea what caused this.
Here’s a photo of the “guts” of the BeerBug after I opened it up so see if some crud from the fermentation might be causing some problems. There was a little yeast but it didn’t seem like enough to produce the weird results. The oscillations happened even after I cleaned up the little bit of material in this photo.
In summary, the performance of the device has been very erratic to the extent it’s not really useful for me right now. Hopefully this can be fixed in software, though so far the cause of the drift and oscillations remains obscure.