Blue laser sensor measures vibrations on engine manifolds

Citation

(2012), "Blue laser sensor measures vibrations on engine manifolds", Sensor Review, Vol. 32 No. 4. https://doi.org/10.1108/sr.2012.08732daa.004

Blue laser sensor measures vibrations on engine manifolds

Article Type: Mini features From: Sensor Review, Volume 32, Issue 4

The optimisation of internal combustion engine operation is becoming increasingly important. For engine management purposes, a whole series of measurements need to be carried out.

The temperature of the exhaust gas, for example, is an important parameter, which is measured using a thermocouple mounted within the engine manifold. To verify the way it is mounted, it is necessary to examine its propensity to vibrate, as well as the mechanical rigidity of the structure.

For this type of application, Micro-Epsilon’s new optoNCDT 1700BL blue laser sensor offers specific benefits (Figure 10). Due to the high temperatures in the exhaust gas flow, the thermocouple becomes red-hot or self-fluorescing. With red-hot glowing objects, a conventional red laser has a high signal interference from the surface of the thermocouple, because it emits the same or very near wavelengths of light as the red laser. However, the blue laser works at a wavelength of 405 nm, which is far from the red part of the visible spectrum. This means it is easier to filter this type of emitted light from the thermocouple, which ensures very stable signals.

Figure 10 Blue laser measures vibration on hot engine manifolds

A narrow slit provides sufficient free space for the optics. The high ambient temperatures are effectively reduced for test operation by using a protective plate or shield, whilst a blower ensures clean optical conditions and cooling.

Due to the sensor’s high speed sampling frequency (2.5 kHz), the expected vibrations on the thermocouple can be accurately measured and then easily evaluated via digital interface to a PC.

Micro-Epsilon’s optoNCDT 1700BL series of Blue Laser Sensors operate on the laser triangulation measuring principle and use blue (violet) laser technology. As well as for applications on automotive engine manifolds and brake discs, the sensors are also ideal for measurements on hot, glowing metals in steel processing applications, as well as for measuring organic materials such as skin, foodstuffs, plastics, veneers and wood.

Unlike a red laser, the blue laser light does not penetrate into the measuring object because it has a lower intensity laser spot and therefore offers more stable, precise measurements on targets that conventional red laser sensors have difficulty measuring.

The sensors are equipped with high-end optical lenses, intelligent laser control and evaluation algorithms. The sensors are suitable for red glowing metals up to 1,600°C, and for silicon up to 1,150°C.

The optoNCDT 1700BL operates using the laser triangulation principle. A laser diode projects a visible point of light onto the surface of the target object. The light reflected from this point is then projected onto a CCD array. If the target changes position with respect to the sensor, the movement of the reflected light is projected on the CCD array and analysed to output the exact position of the target. The measurements are processed digitally in the integral controller. The data is output via analogue (I/U) and digital interface RS422 or USB.

For more information on Micro-Epsilon’s optoNCDT 1700BL, please call the Micro-Epsilon sales department on 0151 355 6070 or e-mail: info@micro-epsilon.co.uk