Final Solution

Our final solution utilizes the URM14, a precision ultrasonic sensor to measure the distance to a floating object within the brewing liquid. As the density of the liquid changes during the fermentation process, so does the position of the floating object. The sensor detects this shift in height, which corresponds to the specific gravity of the liquid. Coupled with a built-in thermometer, the sensor also satisfies the requirement for temperature measurement.

Link to our Github Repository

Top picture from: https://wiki.dfrobot.com/URM14_RS485_Precision_Ultrasonic_Sensor_200KHz_SKU_SEN0358#target_6

Wiring Schematic

Background Image from Unsplash

Final Testing Data

When conducting our final tests we used the methodology of adding sugar in increments then measuring the change in bobber height in order to calculate the accuracy. For each increment of adding sugar we measured the bobber height four times by taking the average over 60 seconds with a measurement every second. By using our product fully assembled to make these tests we are able to make conclusions about the precision and accuracy of our device as it compares to our specifications.

Calibration

The calibration of our device requires two simple steps. First the user must take an initial specific gravity measurement using a physical hydrometer. Next the user must update this measurement within the calibration script upon starting up the device. The device will not run without this measurement and will continue to prompt the user for this information until it is received.

Measurements

The precision of our device can be determined through our final testing results by comparing the accuracy of each test. The four tests that were performed remained within  .0005 g/mL of each other which displays that our device has a high level of precision. The accuracy of our device can be confirmed by comparing our final results of a long term brew to a physical hydrometer reading. After adding yeast to a sugar water solution we were able to find that the final specific gravity output from our device matched the actual final specific gravity measured by a physical hydrometer.

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