National Instruments NI EDIDS-2400 Series, User Manual, Page: 176 / 314

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Figure 4.11.d, 6+1 (retarded) crankshaft trigger wheel tooth numbering
Encoder Patterns
Pattern Description:
Encoder patterns have N evenly spaced teeth on the crankshaft with a separately sensed single reference (index,
EncZ ) tooth on the crankshaft or camshaft. The rising edge of the reference must occur between the same two
crankshaft teeth rising edges each and every cycle. The EPT ENC function can be configured to track 360 or 720
degrees. When tracking 360 degrees, the reference tooth is located on the crankshaft, yet is internally connected to
the CamSig input of the EPT function via the EncZ digital input. When tracking 720 degrees, the reference tooth is
located either on the crankshaft or on the camshaft. When located on the crankshaft, then an additional cam phase
signal must be present in order to mask (using EncZMask ) every other crank reference, such that every other crank
reference is allowed to pass through to the CamSig input of the EPT function. Encoder style patterns are a very
common form of engine position tracking in both production and research engine control systems.
Production Engine Encoder Patterns:
In production engines, an encoder pattern will typically consist of a trigger position sensor sensing a relatively low
resolution crankshaft trigger wheel. The camshaft trigger position sensor is sensing a single tooth on the cam. For
this configuration, the cam position signal should be routed to the DI Driver System EncZ signal via the Digital Input
Setup window, and the EncZMask button of the EPT tab should be set to EncZ Passed . For this configuration, the
rising edge of the cam signal should occur as close as possible to the midway point between two crank signals. The
system designer should also ensure that the camshaft lash due to stretching of the camshaft belt or chain during
acceleration or deceleration will not cause the cam signal to move with respect to the crank signals by more than
half of the crank tooth spacing. For this reason, production systems will use a low resolution crank trigger wheel. The