Inertia X1 is a physical instrument — a spring-driven torsional pendulum — but its intelligence lives in the app. The app is what transforms the raw gyroscope signal into a reliable swingweight measurement, guides the user through calibration, archives results, and allows raw data to be exported for in-depth diagnostic analysis. This article describes how it is organised and what it makes possible.
How to Access the App
The Inertia X1 app is not downloaded from traditional stores. Access is obtained by scanning the QR code on the instrument: in a single step, the smartphone recognises the device, automatically loads the calibration parameters specific to that unit, and launches the app. Nothing needs to be entered manually.
This system ensures that every instrument always operates with its own factory configuration, eliminating setup errors at the root.
The Structure of the App
The app is organised into four main sections, accessible from the navigation bar at the bottom: Measure, Calibrate, Archive and Info.
Measure
This is the main screen, used at every session.
When the instrument is ready, the user rotates the support to the angular stop, presses the Start button and releases. The app acquires the gyroscope signal during oscillation, automatically analyses the data, and within a few seconds displays the swingweight value along with measurement quality indicators: stability, symmetry, damping and overall reliability.
Each measurement can be associated with a specific racket saved in the database, or taken as a free measurement. If the measurement is associated with a frame saved in the database, the app allows you to measure both the Swingweight and Twistweight. A reliability indicator immediately indicates whether the measurement is considered valid or whether it should be repeated.
Calibrate
Calibration is the step that allows the app to translate the oscillation period into a swingweight value. It is performed using the two calibration samples supplied with the instrument — two configurations of the same calibration bar: a lighter one (Sample A) and a heavier one (Sample B, obtained by screwing the included bolt onto the bar).
The app offers two modes:
Standard Mode — A step-by-step guided procedure requiring three measurements of Sample A, three of Sample B, and a final verification measurement with Sample A. Upon completion, the app compares the verification result with the nominal value and certifies the validity of the calibration. This is the recommended mode for daily use.
Modalità Esperto Designed for users who want more granular control. It allows you to freely choose which sample to mount, to perform as many measurements as you want for each, and to manually discard individual less accurate measurements before confirming the calibration. It is also useful for manually entering sample inertia values, for example when you want to compare results with those from another instrument.
Calibration is linked to the physical instrument, not to the smartphone: as long as the instrument is not moved from its work surface, calibration does not need to be repeated. If the instrument is moved, a new calibration should be performed before resuming measurements. Before starting a measurement, the app displays the digital level — two indicators that allow the user to verify that the instrument is correctly levelled on the work surface.
Archive
The archive is the register of rackets and measurements. Each racket can be saved with its own characteristics — owner, brand, model, weight, balance — and linked to swingweight measurements taken over time.
The last ten complete measurements are stored with all raw data, making it possible to export a detailed diagnostic file. Earlier measurements are archived in summary form, retaining the swingweight value and date.
This structure allows the evolution of a racket to be tracked over time — useful, for example, to verify whether the addition of lead tape has produced the desired effect, or to compare two frames of the same model.
Info and Diagnostics
The Info section contains information about the active calibration, the app version, and the instrument parameters. It also includes the diagnostic file export function: a JSON file with all the raw data from the last session — samples, periods, gyroscope signal, measurement quality indicators for each test — which can be sent to technical support for in-depth analysis in the event of anomalies.
This function was designed to make the instrument's operation transparent: not just a final number, but all the data that led to that number.
Two Platforms, One Experience
The Inertia X1 app is available for both iPhone and Android, but the two versions have different underlying architectures — for a precise technical reason.
iPhone: the Web App in the Browser
On iOS the app runs as a Progressive Web App (PWA): it opens in the Safari browser, behaves like a native app, and can be added to the Home Screen. No download from the App Store is required.
This approach works because Safari on iOS accesses the gyroscope sensor with the same precision and temporal stability as a native app. There is no measurable difference in signal quality between a PWA and a native app on iPhone: iOS users already get the maximum possible precision without installing anything.
Android: the Native App
On Android, the situation is different. We have verified on a wide variety of devices – particularly those with custom interfaces like Realme UI and MIUI – that the Chrome browser introduces temporal variability in the gyroscope signal, the so-calledtremor, which can reduce the accuracy of the oscillation period measurement.
The cause is structural: when a web app requests gyroscope data, the browser delivers it through its own processing cycle, adding variability to the timestamps that has nothing to do with the hardware. On some devices this effect is negligible; on others it can be significant.
For this reason we developed a native Android version of the app, built with Capacitor. The native app accesses the hardware sensor directly, bypassing the browser entirely. The result is jitter reduced by approximately ten times compared to the web version on Android, with higher sampling rates on modern devices.
The Android app installs automatically by scanning the instrument's QR code: if the app is not yet on the device, the QR code initiates the download; if it is already installed, it opens directly loading the instrument's parameters.
Same App, Same Algorithm
Both versions share the same calculation engine — a WebAssembly module that implements the signal analysis algorithm — the same interface, the same calibration procedure, and the same data export format. The difference concerns only the channel through which gyroscope data reaches the algorithm. For the end user the experience is identical.
Updates
App updates are distributed automatically: the PWA on iOS updates itself every time it is opened; the Android app updates by downloading the new version via the QR code or via a link communicated to registered users. No additional action is required.
