By Arnaud Martinez

finessomètre digital
Figure 1. The first prototype (June 2023). Click on the image to see the video.

Here is the progress of the digital "finessomèter". The sensor measures the angle, calculates the finesse then transmits by radio to a receiver which displays it. The idea is to hang the receiver on an elevator to have a display of the air finesse in real time. There is still work to do but the result of the prototype is encouraging!

It is indeed a digital inclinometer which measures the angle between the electronic card and the horizontal. In fact, the sensor has a 3-axis accelerometer and a 3-axis gyroscope. The accelerometer gives the gravity vector when the system is at rest (without disturbances). The gyroscopes give the angular velocities. By integrating the angular velocities of the gyroscope, we obtain the evolution of the angle over time. By merging the two sensors, the angle between the sensor and the horizontal is precisely obtained. Then just calculate the tangent to get the glide angle.

For the moment it's done on a somewhat obscure microcontroller but I'm thinking of migrating to an Arduino so that everyone can follow. The first prototype is built around an MPU6050 sensor, an Nrf24l01+ radio and the controller is an STM8 but I'm thinking of migrating to an Arduino pro-mini.

I power it with a rechargeable NiMh battery in AAA size followed by a Boost converter to provide 3.3v

The receiver is another Nrf24l01+ radio, a TM1637 display, and an Arduino nano, which I will surely also replace with a pro mini.

I want to add an SD card on the receiver to save fineness measurements and make graphs later at home.

Several improvements are possible, like adding a GPS or a wind probe, but at first I want to keep the system simple.

Figure 2. Checking operation. Finesse = 1 / tan (alpha) and alpha is the angle from the horizontal.

 1. We will soon publish detailed plans and instructions for this electronic device, which will remain in the public domain.
2. See also our "finessòmetre" geometric angle meter (gravitational pendulum), used in the late 80s, when measuring the fineness of the mountain was recommended to calculate if we would reach the landing field...