The portable Doctor DK-2 series is an industry standard for cylinder pressure measurement, having built its reputation on reliability, accuracy and ease-of-use. The “Diesel Doctor”, as it is often known, is housed in an extremely rugged plastic case and is fully seal against moisture and dirt. A complete system, including sensors and cables, fits into a convenient shoulder bag about the same size as a camcorder case. Two versions are available. The DK-2 is a single channel unit for measuring cylinder pressure while the DK-2/FV measures cylinder and fuel pressure or vibration traces simultaneously. Both systems use Kistler pressure sensors for long-term reliability and accuracy.
For synchronizing to shaft rotation, two schemes are available. The first uses an inductive pickup that senses a small metal target on the flywheel. This can be permanently wired to a junction box on the engine. This enables straightforward connection of a cable for quick speed and shaft synchronization. For large 2-stroke engines a dual pick-up system is available that compensates for changes in rotational speed during each revolution of the engine. This provides increased accuracy when the engine is, for example, driving a propeller shaft directly. The second scheme is ideal for service work and comprises an optical pickup with a small fibre-optic extension. This will sense any light-colored marker on the flywheel. It is often possible to use an existing mark and so it is not necessary to stop the engine before taking a set of readings. Operation of the system is simple. The engine configuration (2-stroke/4-stoke, V/inline, etc) is entered and this is stored under the engine name. Hence, this is a “once-only” task. To take a measurement, the operator connects the pressure and vibration sensors to the appropriate cylinder, and presses the GO button on the Engine Processor Unit (EPU). The screen indicates the progress of the measurement and, once complete, the operator just moves the pressure sensor to the next cylinder and presses GO again. Key parameters such as power, angle of Pmax, etc. are shown on the screen. The system is easily operated by one person, and the time to measure a typical engine is just ten minutes or so.
Once all cylinders have been measured, results are transferred to a PC via the serial port on the unit. The detailed graphs and full analysis options of the standard Doctor software are then available to examine results.
Doctor Portable Systems Technical Info
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