SprayQuantAI® SQA2

SprayQuantAI® SQA2 is the two-channel configuration of the SprayQuantAI® measurement platform. It combines the LSS2 optical probe with the IMEA control unit for time-resolved measurement and evaluation of individual droplets or particles.

SQA2 records two synchronized light-scattering signals from each detected particle event. Compared with the single-channel SQA1 configuration, the additional detector channel provides more optical information about the same particle passage and supports more advanced evaluation and validation concepts.

Depending on the configured measurement method, the synchronized signals can be evaluated using classical signal-processing methods or AI-based algorithms.

SQA2 consists of the LSS2 optical measurement probe, the IMEA control and acquisition unit, and the SprayQuantAI® measurement and evaluation software.

Component	SQA2 Configuration	Function
Optical probe	LSS2	Generates the measurement region and detects time-resolved scattered light
Detector channels	2	Records two synchronized optical signals for each detected particle event
Control unit	IMEA	Signal acquisition, processing, calculation and process communication
Evaluation	SprayQuantAI®	Individual-event evaluation using classical or AI-based methods

The LSS2 optical probe generates a specifically shaped illumination field. When a droplet or particle passes through the measurement region, it produces time-dependent scattered-light signals that are detected by two optical channels.

The motion of the particle through the spatial illumination field transforms geometrical information into temporal signal information. Both detector channels observe the same particle passage from their defined optical configurations and provide synchronized signal waveforms.

IMEA acquires both signals with high temporal resolution and provides them to the configured SprayQuantAI® evaluation method.

The defining feature of SQA2 is its two synchronized optical detector channels. Both channels record time-resolved information from the same droplet or particle event.

The second detector channel is not simply a duplicate measurement. It provides additional optical and temporal information that can be used to improve the evaluation of individual particle events.

Depending on the optical configuration and calculation method, the two-channel information can support:

• additional time-shift information
• more detailed characterization of individual particle events
• comparison of independently measured signal features
• event-level plausibility checks
• rejection of implausible particle events
• additional input information for AI-based models

In classical operation, SQA2 evaluates characteristic features of the two time-resolved detector signals using defined physical and geometrical relationships.

Measured time intervals can be connected to known distances within the optical measurement geometry. In simplified form, particle velocity follows the time-of-flight relationship:

Here, Δx is defined by the optical geometry and Δt is measured from the particle signal. Once velocity is known, additional temporal signal features can be converted into spatial particle information.

The second detector channel provides additional information that can be compared with the results from the first channel. This makes it possible to assess the consistency of individual particle events before statistical spray parameters are calculated.

SQA2 can also use machine-learning models to evaluate individual particle events. In this case, the model can use information from one or both synchronized detector signals, depending on the model architecture and measurement task.

The additional detector channel increases the amount of optical information available to the AI model. Signal shapes, amplitudes, characteristic positions, time shifts, and relationships between the two channels can therefore contribute to the prediction of particle properties.

The appropriate AI model depends on the optical configuration, material, particle or droplet properties, operating range, and required output parameters.

Depending on the selected optical configuration and evaluation method, SQA2 can provide information such as:

• droplet or particle size
• droplet or particle velocity
• droplet or particle number
• particle event rate
• size distributions
• velocity distributions
• time-dependent spray trends
• spray stability indicators
• statistical process parameters

The individual-event results can be accumulated over defined measurement intervals to describe the statistical behavior of the complete spray.

One advantage of the two-channel configuration is the possibility of comparing information obtained from synchronized detector signals for the same particle event.

Signals that do not fulfill defined physical or statistical criteria can be identified before they contribute to the calculated spray distributions. This is useful because not every detected optical event necessarily corresponds to an ideal particle passage through the measurement region.

Possible causes of implausible events include unfavorable particle trajectories, overlapping particles, incomplete signals, or insufficient signal quality.

The LSS2 is the two-channel optical probe used by SQA2. It generates the optical measurement region and provides two synchronized time-resolved light-scattering signals.

The probe is connected to the IMEA control unit by optical fibers, allowing the measurement location and acquisition electronics to be physically separated.

Parameter	LSS2
Measurement principle	Time-resolved light scattering
Active detector channels	2
Wavelength	405 nm
Dimensions	182 × 74.9 × 32 mm
Compatible control unit	IMEA

Technical details for LSS2

The IMEA control unit provides synchronized two-channel signal acquisition, calculation, system control, host communication, and interfaces for industrial process integration.

IMEA receives the optical signals from LSS2, digitizes and processes the time-resolved waveforms, performs the configured SprayQuantAI® calculations, and provides the resulting measurement values to the software or external systems.

Parameter	IMEA
Optical signal inputs	2
Host communication	Ethernet
Digital inputs	4 × 24 V
Digital outputs	4 × 24 V
Analog inputs	4 × 4–20 mA
Analog outputs	4 × 4–20 mA
Trigger	Trigger input and output
Dimensions	251 × 211 × 109 mm

Technical details for IMEA

SQA2 can continuously evaluate individual droplets or particles during an operating spray process. Measurement results can be accumulated over defined time intervals to generate continuously updated spray parameters.

Changes in particle size, velocity, number, distributions, or other statistical values can therefore be tracked over time and compared with reference process conditions.

The two-channel configuration also provides additional information for checking the consistency of individual measurements before they are included in the process statistics.

SQA2 can be integrated into laboratory test rigs, development systems, atomizers, spray equipment, and industrial production processes.

IMEA provides communication and process interfaces for exchanging measurement data and status information with external equipment.

• Ethernet communication
• digital inputs and outputs
• 4–20 mA analog inputs and outputs
• external trigger input and output
• transfer of calculated process values
• integration into monitoring and automation systems

This allows SprayQuantAI® measurement information to become part of an existing industrial monitoring or process-control environment.

• paint and coating spray characterization
• spray gun development
• nozzle characterization
• atomizer development
• rotary atomizer measurements
• droplet size and velocity measurements
• advanced spray diagnostics
• spray stability monitoring
• quality assurance
• fluid-mechanics research
• industrial spray monitoring

SQA2 can be adapted to the measurement task. The appropriate configuration depends on the spray, atomizer or nozzle, material properties, expected particle size and velocity, concentration, installation environment, and required measurement results.

Possible adaptations include:

• optical probe geometry
• working distance
• measurement region
• detector geometry
• mechanical mounting
• laser and optical configuration
• signal-processing parameters
• measurement software
• AI models
• industrial interfaces

For industrial applications, the adaptation of the optical probe to the spray gun, nozzle, rotary atomizer, or production equipment can form an important part of the complete measurement solution.

Both systems use the same fundamental SprayQuantAI® individual-event measurement concept. The main hardware difference is the number of synchronized detector channels.

Parameter	SQA1	SQA2
Optical probe	LSS1	LSS2
Control unit	ZEON	IMEA
Detector channels	1	2
Data per particle event	One time-resolved signal	Two synchronized time-resolved signals
Evaluation	Individual-event evaluation	Individual-event evaluation
Main characteristic	Compact optical configuration	Additional optical information and validation possibilities

SQA1 is the more compact configuration when one detector channel provides sufficient information for the measurement task. SQA2 is intended for applications where the additional synchronized detector signal provides useful information for classical calculation, event validation, or AI-based evaluation.

SQA2 and ParticleTensorAI® PTA2 use the same LSS2 and IMEA hardware platform. The difference lies in how the recorded signals are acquired and evaluated.

SQA2 focuses on individual droplet or particle events. Each event is identified and evaluated separately before the results are combined into statistical spray parameters.

PTA2 instead retains synchronized signal sequences over a defined acquisition interval and processes them using the ParticleTensorAI® tensor-based AI approach.

The measurement technology behind SQA2 builds on the Time-Shift-Time-of-Flight approach for optical characterization of droplets and particles. The method uses precisely measured temporal structures within light-scattering signals to determine particle properties.

Machine-learning-based evaluation provides an additional method for extracting information from individual measured waveforms and can complement the classical physical evaluation.

[1] Schaefer, W.; Li, L.; Stegmann, P.; Terada, M. Technical Report on the TSTOF Measurement Method: Technical Basics, Historical Development, and Comparison with Other Laser-Based Measurement Methods. Photonics 2026, 13(1), 56. https://doi.org/10.3390/photonics13010056

[2] Schaefer, W.; Li, L. Particle characterization by analyzing light scattering signals with a machine learning approach. Applied Optics 2024, 63(29), 7701–7707. https://doi.org/10.1364/AO.531346

• SprayQuantAI® Overview
• SprayQuantAI® SQA1
• LSS2 Optical Probe
• IMEA Control Unit
• ParticleTensorAI® PTA2

For an application-specific SQA2 configuration, contact ai-quanton with information about the spray, atomizer or nozzle, material, expected droplet properties, process conditions, and required measurement results.