Accuraspray G3

This is the latest iteration of systems for the in-situ, real-time analysis, recording and display of thermal spray or metallization process characteristics. A-PC based controller digitizes the video and sensor signals, and sophisticated software performs the necessary calculations, delivering easy to interpret results and data through the system’s user interface.

During operation, the sensor head is aimed at the spray plume from a predetermined and repeatable position and the following eight conditions are recorded:

Accuraspray Sensor Head and Controller Showing the Two Main Components of the Instrument: the PC Based Controller and Sensor Head (10 m Cable is not Shown)
  1. Average particle temperature
  2. Average particle velocity
  3. Position of spray plume
  4. Width of the spray plume
  5. Maximum luminosity of the spray plume
  6. Overall intensity of the spray plume
  7. Substrate temperature (optional)
  8. Internal sensor head temperature

Values of all these parameters are continuously recorded, displayed and compared on-screen against user-adjustable acceptance intervals. An alarm can be triggered through digital I/O ports according to a user-adjustable alarm protocol. A standard 10/100 Ethernet port allows the instrument to be polled and controlled by advanced spray consoles such as Sulzer Metco’s Multicoat using a standard TCP/IP protocol.

The system is also equipped with a feedback algorithm that will suggest, for plasma spray, the optimal parameter alterations necessary to bring particle temperature and velocity back within acceptable values.

Principle of Operation

Figure 2: Particle Temperature and Velocity Measurement Principle Simple, time-shift cross-correlation yields a very precise measurement of the time delay from which the velocity can be calculated since the gap between the measuring points is a precisely known constant. In addition, the detectors are filtered at two different colors, allowing the mean particle temperature to be measured using the very well-known twin wavelength pyrometry principle (assumes that the emissivity of the particles is the same for the two wavelengths).

One advantage of this method is that the value of the cross-correlation (between 0 and 1) gives an indication of the validity of the temperature measurement. A strong correlation between the two signals (above 0.6, for example) means that the two detectors are seeing the same particle population which is essential for the twin wavelength pyrometry to work properly.

Accuraspray features a dual fiber optical device that "sees" the flow of particles at two different points along the spray stream. The signal from the down-stream detector is very similar to the first one but delayed in time because it comes from the same particles detected a few millimeters apart.