iSpindel vs Hydrometer and Gravity

iSpindel

This device, in my view, is genius.

It’s a small tube with a watertight lid with a battery and electronics inside. When placed into a fermenter with the wort, it can relay, almost live, the temperature and gravity readings via WiFi. The rechargeable battery is designed to last many weeks and has easily lasted longer than any of my fermentations thus far.
It manages this by “sleeping” most of the time and waking up every 15 minutes for just long enough to send the latest data. The genius part is how it measures gravity. The heaviest part of the guts is the battery. It is fixed inside the tube towards one side and near the bottom. This offset weight results in the device floating with the same side upwards and at an angle. The angle/tilt can vary depending on the density of the wort. Initially when there is plenty of sugar still to ferment, the density will be higher and the tilt will be less. As more sugar is turned to alcohol, the density drops and the device tilts to a more upright position. It has a sensor that, after calibration, can measure the angle of the device. This can be used to calculate the density and thus the gravity. In my set up, the data is received and displayed by a dashboard server. This shows the current readings and charts temperature and gravity history. I will have an detailed article about this in the future.

The iSpindel is an opensource device you can make yourself. More information can be found on the iSpindel website. Pre-built and calibrated versions are also available. It’s based on a commercial product named Tilt.

Hydrometer

This is a tool that measures the density or specific gravity of wort or must. It is a long glass tube with a weight at the bottom that helps it float upright. It can sink deeper in lighter fluids and vice verse in denser ones. There is a scale along the length of the tube that allows the reading at base of the meniscus to be read. It gives the same gravity data as the iSpindel but involves drawing off liquid to take the measurement. This makes it very labour intensive by comparison. I usually only use my hydrometer to measure the Initial/Original gravity of the cider I make. It gives a pretty good idea of the final ABV because the yeast I use is pretty reliable for fermenting down to around 1.000 – 1.002.

Specific, Original, Initial, Target and Final Gravity

Where would we be without gravity? In space probably. Joking aside, when starting out in brewing, this is possibly the most important measurement we can take. Yes, temperature, pH, volume and other things *are* important but gravity can tell us a lot.

Specific Gravity: this is the density of a fluid compared to water. When taken before fermentation has started it is called the Initial or Original Gravity (OG). If we have idea of what the gravity should be at the end of fermentation, this would be our Target Gravity. And finally – pun intended – we have the Final Gravity. This is the reading when fermentation has ended and the gravity has not changed for two days. Target and Final gravity sometimes don’t line up, this is normal. Yeast sometimes does better or worse than expected and the actual amount of fermentable sugar may not have been what we originally thought. Hey, if you can still drink it, it’s just a learning point, not a fail!

More information on Wikipedia