Custom Calibration
RAPT Pill Hydrometer & Thermometer - Custom Calibration Guide
Last updated
RAPT Pill Hydrometer & Thermometer - Custom Calibration Guide
Last updated
Warning! Custom Calibration is for advanced users only.
Typically Advanced Calibration is accurate enough for all but the most extreme use cases.
This mode can provide the most accurate readings across a wider range than the other calibration modes.
Only proceed if you are comfortable with spreadsheets and complex curves. If you are working with solutions with gravities higher than 1.080, then custom calibration is advised.
For Custom calibration, you will need to take readings at various gravity points roughly 10 gravity points apart, and make a note of the angle of the Pill at each point. We recommend readings from 1.080 down to 1.000, 10 points apart (so, 1.080, 1.070, 1.060 etc). Note that it does not matter if the gravity readings are not exactly 10 points apart, as long as the gravity reading is correct. Use of a hydrometer that is known to be accurate is quite important.
To perform Custom Calibration, it is easiest to start with the strongest solution and dilute to progressively weaken the solution. It is important to use a calibrated hydrometer to ensure accurate gravity readings
Plug your Rapt Pill into a charger or computer with a USB-C cable (not included) or place on the wireless charger (if the wireless charging kit is installed)
On your smart phone or tablet, open your WiFi settings and connect to the RAPT Pill XXXX access point using the password "kegland1". You may not need to enter the password if you have previously connected your device to the Pill WiFi
Once the RAPT Pill Access Portal is open on your phone or tablet, navigate to the Calibration tab
Place the Pill in the first solution of known gravity. Wait for the angle to stabilise, then make a note of the angle and the gravity
Repeat this step for solutions of different gravity, making a note of the angle and the gravity at each step. It is easiest to dilute the starting solution in steps of approximately 10 points. Finish with a reading in a solution with a gravity of 1.000 (IE water)
Once you have sufficient readings, the angle and the gravity need to be entered on an Excel spreadsheet (or similar such as Google Sheets) as a graph with gravity on the ‘y’ axis and angle on the ‘x’ axis. The more readings you take, the more accurate this calibration will be. We recommend a minimum of 6 samples, with 10 or more providing a greater degree of accuracy.
When you have created the graph, create a polynomial trend line onto the graph with the degree of the polynomial being at least one less than the number of data points. If the trend line creates an irregular curve (such as not passing through the data point at 1.000 correctly or not following a polynomial shape) reduce the number of data points (ensuring that there are still more data points than the degree of the polynomial) until the curve matches.
This is a sample only
With 10 data points, a polynomial degree between 5 and 8 will typically give the best results.
Copy the equation of the trend line that is generated once this is done.
Paste this equation into the field provided on the Custom Calibration screen (In Google Sheets, set your label to Use Equation).
This will look similar to this:
y = 0.0000023109x5- 0.0005741632x4+ 0.0568746764x3- 2.8119846525x2+ 71.1087310405x + 265.6578215178 This is a sample only – DO NOT USE THIS EQUATION AS IT WILL NOT BE ACCURATE
Substitute x in this equation with “angle^” thus:
y = 0.0000023109angle^5- 0.0005741632angle^4+ 0.0568746764angle^3- 2.8119846525angle^2+ 71.1087310405angle + 265.6578215178
This is a sample only – DO NOT USE THIS EQUATION AS IT WILL NOT BE ACCURATE
Paste this equation into the field in your Custom Calibration to complete the calibration.
Congratulations! Your Pill is calibrated and ready to go.
Your Pill is now calibrated and ready to use!
