Transmitted light measurement systems for spray jet monitoring (non-Ex area)

In transmitted light operation, spray jet monitoring enables precise real time supervision of spraying processes. In the laser fork version, even individual droplets can be reliably detected. For evaluating spray jet geometry, single channel, dual channel, three channel and multi channel laser variants are available, allowing continuous monitoring of the position, shape and stability of the spray jet.

A pronounced, collimated laser light curtain in combination with a high resolution line detector captures the cross section of the spray jet across its entire width. This makes it possible to detect changes in the spray pattern, irregularities in droplet distribution or nozzle misalignment at an early stage, thereby reliably preventing process deviations.

See also our brochure on inline spray jet monitoring: 



If a larger distance between the sensor and the spray jet to be measured is required due to system constraints, a transmitted light system becomes indispensable.
Using the SPECTRO-1-CONLAS electronics and the A-LAS-N series frontends, laser spots ranging from 0.3 mm in diameter up to 16 mm × 2 mm are available. The laser spot is aligned with the spray cone so that the spray jet is fully captured. The closer the laser light curtain is positioned to the nozzle outlet, the greater its influence on the measurement signal. When additional monitoring of the spray cone geometry is required — for example, the spray cone opening angle or deviations from the ideal symmetry axis — at least three positions within the spray cone typically need to be monitored.
The compact laser spray jet monitoring system SI-JET-CONLAS3-T-d1.5 (transmitter unit) + SI-JET-CONLAS3-R (receiver unit and evaluation electronics) features three collimated laser beams that can detect spray cones with small opening angles even in very confined spaces.
Using the SCOPE function of the PC software, the signal curves of the three channels can be analyzed under spray jet influence. This allows conclusions to be drawn regarding both spray jet intensity and spray jet geometry.  If a three channel system is insufficient for spray jet analysis, a complete cross section of the spray cone can be captured and evaluated using laser line transmitted light sensor technology.
The collimated laser light curtain directed at the spray jet passes through the spray cone and reaches a line detector element on the receiver side. The video signal provided by the line detector indicates the local attenuation of the laser light caused by the spray cone.
Using specialized algorithms, individual spray jets within the spray field can be located, and their peak height and exact position within the spray jet profile can be determined. For a single spray cone, its symmetry and spray jet intensity can also be precisely evaluated. 

Single channel inline transmitted light systems for monitoring individual droplets

In both the pharmaceutical industry and in electronics manufacturing (e.g., selective soldering), liquids are applied to a substrate in discrete packets (droplets), for example using a piezo nozzle or an electromagnetic nozzle.
The task of the spray jet monitoring system is to monitor the amount of liquid applied to the substrate. The system counts the droplets and determines the size of each droplet (width and length) using a laser light curtain.
Comprehensive PC software is available for parameterization of this measurement system as well. Using the integrated SCOPE function, a droplet sequence can be recorded, for example. For this measurement setup, an A-LAS-CON1 control unit was used in combination with an A-LAS-F12 laser fork light barrier.