External tools: Rosette computation

The Rosette Computation tool is a standalone NVGate add-on that transforms raw strain gauge rosette signals into principal stress and principal stress angle time histories. It reads a time-domain measurement directly from the NVGate Player, performs the Mohr's circle computation sample by sample, and writes a new measurement back into the same NVGate project — ready to be analysed, displayed or exported like any other signal.

Downloads

File	Description
Download here	Standalone executable + all dependencies. Unzip and copy to C:\OROS\NVGate data\Links\
NVGate: Demo signal to test	Demo NVGate measurement with 3 rosette channels (rectangular, steel)

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Principle

A strain gauge rosette is a set of three strain gauges bonded close together on a surface and oriented at fixed angular offsets from each other. Because a single gauge only measures the normal strain in one direction, at least three gauges at known angles are needed to fully characterise the two-dimensional strain state at that point.

Once the three principal strains (ε₁, ε₂) and their orientation θ are known, the principal stresses (σ₁, σ₂) are derived using the plane-stress constitutive relations for a linear isotropic material.

The tool implements this calculation sample by sample over the full length of the signal, producing two additional time channels:

Output channel	Physical quantity	Unit
Principal Stress Magnitude	Maximum principal stress σ₁	Pa
Principal Stress Angle	Orientation of σ₁ w.r.t. gauge A	rad

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Supported Rosette Configurations

Three standard rosette layouts are supported:

Configuration	Gauge angles	Typical use
Rectangular / 45°	0° — 45° — 90°	General-purpose; most common in industry
Delta / 60°	0° — 60° — 120°	Equiangular rosette; more isotropic sensitivity
0° / 120° / 240°	0° — 120° — 240°	Alternative delta layout; same calculation as 60°

Mathematical formulas

Rectangular rosette (0° / 45° / 90°)

With εA, εB, εC being the strains measured by gauges A, B, C respectively:

${\text{Center}}={\frac {\varepsilon _{A}+\varepsilon _{C}}{2}}$

${\text{Radius}}={\frac {1}{\sqrt {2}}}{\sqrt {(\varepsilon _{A}-\varepsilon _{B})^{2}+(\varepsilon _{B}-\varepsilon _{C})^{2}}}$

$\varepsilon _{max}={\text{Center}}+{\text{Radius}}\qquad \varepsilon _{min}={\text{Center}}-{\text{Radius}}$

$\sigma _{1}={\frac {E}{1-\nu ^{2}}}\left(\varepsilon _{max}+\nu \,\varepsilon _{min}\right)$

$\theta ={\frac {1}{2}}\arctan 2\!\left(2\varepsilon _{B}-\varepsilon _{A}-\varepsilon _{C},\ \varepsilon _{A}-\varepsilon _{C}\right)$

Delta rosette (0° / 60° / 120° and 0° / 120° / 240°)

${\text{Center}}={\frac {\varepsilon _{A}+\varepsilon _{B}+\varepsilon _{C}}{3}}$

${\text{Radius}}={\frac {\sqrt {2}}{3}}{\sqrt {(\varepsilon _{A}-\varepsilon _{B})^{2}+(\varepsilon _{B}-\varepsilon _{C})^{2}+(\varepsilon _{A}-\varepsilon _{C})^{2}}}$

$\varepsilon _{max}={\text{Center}}+{\text{Radius}}\qquad \varepsilon _{min}={\text{Center}}-{\text{Radius}}$

$\sigma _{1}={\frac {E}{1-\nu ^{2}}}\left(\varepsilon _{max}+\nu \,\varepsilon _{min}\right)$

$\theta ={\frac {1}{2}}\arctan 2\!\left({\sqrt {3}}\,(\varepsilon _{B}-\varepsilon _{C}),\ 2\varepsilon _{A}-\varepsilon _{B}-\varepsilon _{C}\right)$

Note: The atan2 function is used instead of atan to correctly handle all quadrants, including the case εA = εC (zero denominator).

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Requirements

Item	Requirement
NVGate version	V17 or higher
Signal format	OSFF measurement directory (NVGate V17+) or legacy .oxf
Signal type	Time-domain (static or dynamic channels)
Number of input channels	3 strain gauge channels (any sampling rate)
Operating system	Windows 7 / 10 / 11 (32-bit Python runtime bundled)
NVGate running	Yes — the tool connects to NVGate via NVDrive to read the active player path and refresh the Project Manager

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Installation

Method 1: Copy the .exe to the NVGate Links folder (recommended)

1. Download RosetteAddon.exe (see Downloads below).
2. Copy the entire RosetteAddon/ folder to the NVGate external tools directory:

   C:\OROS\NVGate data\Links\

3. The tool will appear automatically in NVGate's Tools tab at next startup.

Method 2: Run the .exe directly

Double-click RosetteAddon.exe from any location. NVGate must be open and a signal must be loaded in the Player.

Note: The executable is self-contained — no Python installation or additional libraries are required on the target PC.

Usage

Step-by-step

1. Open NVGate and load the measurement containing the rosette strain gauge channels in the Player.
2. Launch RosetteAddon.exe (from the Tools tab or directly).
3. In the Signal Channels card, select which NVGate input corresponds to each gauge:
   • ε A → gauge oriented at 0°
   • ε B → gauge oriented at 45° (or 60°)
   • ε C → gauge oriented at 90° (or 120°)
4. In the Material Properties card, enter the material constants:
   • Young's modulus E — in Pa (e.g. 210000000000 for steel, 70000000000 for aluminium)
   • Poisson's ratio ν — dimensionless (e.g. 0.3 for steel, 0.33 for aluminium)
5. Select the Rosette Type matching your sensor geometry.
6. Click COMPUTE.
7. The tool reads the signal, computes the rosette, and writes a new measurement named <original_name>_rosette in the same NVGate project.
8. NVGate's Project Manager is refreshed automatically — the new measurement appears immediately.

Output measurement

The output measurement is written in the same NVGate project directory as the input, with the suffix _rosette appended to the original measurement name.

Example:

C:\OROS\NVGate data\Projects\MyProject\
  ├── Measurement1\               ← original (3 strain gauge channels)
  └── Measurement1_rosette\       ← created by the tool (5 channels)

The output measurement contains all the original channels plus the two computed channels:

Channel name	Content	Unit	Physical quantity
(original channels)	Raw strain data, unchanged	µε	Strain
Principal Stress Magnitude - A_B_C	σ₁ time history	Pa	Pressure
Principal Stress Angle - A_B_C	θ time history (orientation of σ₁)	rad	Plane Angle

The sampling rate, duration, and all device metadata are preserved from the input channels.

If the output measurement already exists (from a previous computation), it is automatically deleted and recreated. If it cannot be deleted (e.g., currently open in NVGate), a timestamped name is used instead.

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Typical material properties

Material	Young's modulus E (Pa)	Poisson's ratio ν
Steel (structural)	210 × 10⁹	0.30
Stainless steel	193 × 10⁹	0.28
Aluminium alloy	70 × 10⁹	0.33
Titanium alloy	110 × 10⁹	0.34
Cast iron	160 × 10⁹	0.26
Copper	120 × 10⁹	0.34

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Version history

Version	Date	Changes
1.000b	2026-04	Public release. Supports rectangular (45°) and delta (60°/120°) rosettes. Compatible with NVGate V17 OSFF measurement format. Dark UI theme.
—	2024-11	Internal prototype (oxf format, NVGate V12–V16)