For a meaningful, precision indicating measurement, firstly the chain of measurement instruments has to be highly accurate (i.e. pressure trans- ducer-amplifier-indicating device) and secondly, the measurement value has to be unambiguously and accurately assigned to the crank angle. The new optical AVL Angle Encoder 365X is eminently suitable for the job. Based on the established 364X, this X-type angle encoder was developed mainly for installation in the powertrain between the engine and the dynamometer.
The new method based on the transmission light principle means that the system is not affected by interference light which ensures successful indicating measurements even on high revving engines.
Exact acquisition of the crank angle is necessary because crank angle multiplication is needed for a high-resolution indicating measurement (such as injection tests, knock detection, etc.). The marker disk therefore has to be precision-manufactured. It has 360 or 720 slits for the angle information. The crank angle resolution can be increased with the AVL indicating devices of the IndiAdvanced series or by using multipliers up to 0.025 deg CA. Because the steel marker disk of the 365X Set is cut by laser, the deviation from one anlge mark to the next one is less than 0.03°CA maximum. The optical pick-up of the 365X is installed at the crankcase next to the crank shaft where enormous loads occur in the shape of vibrations (>500g), high temperature (120°C) and electrical disturbances. The single-track method in which the trigger is integrated in the angle mark track, means that the marker disk can be smaller and clamped more tightly. It then experiences fewer loads. AVL Angle Encoders are the only ones on the market in which the pickup and electronics are physically separated, because that is the only way to overcome the problem of the high loads described above over a long period of time even at extremely high engine speeds – the limit is greater than 20,000 rpm.