National Instruments NI DIDS-2103, Руководство пользователя

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NI DIDS-2100 Series User Manual | © National Instruments | 111
Encoder
EPT Enc 2
EPT Enc 4
Encoder patterns have N evenly spaced teeth on the
crankshaft with a separately sensed single reference
(index) tooth on the crankshaft or camshaft. The rising
edge of the reference must occur between the same
two crankshaft teeth rising edges each engine cycle.
The EPT Encoder function can be configured to track
360 or 720 degrees. When tracking 360 degrees,
the reference tooth is located on the crankshaft, yet
is directed to the CamSig input of the EPT function.
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. This
would cause the crank encoder pattern to effectively
generate twice the teeth between each reference tooth
seen by the EPT function.
Table 4.6.a, Supported EPT Patterns
Brief Glossary of EPT Function Terms
CAD: Crank Angle Degrees. There are 360 CAD per two stroke cycle or one crankshaft rotation. There are 720 CAD
per 4-stroke cycle, or two crankshaft rotations. In a 4-stroke engine, the camshaft completes exactly one rotation per
two rotations of the crankshaft. There are two strokes of the piston (up and down) within the cylinder during a single
rotation of the crankshaft. A single stroke of the piston covers 180 CAD.
EXTRAP: The single numerical digit suffix of each EPT function selection refers to the level of EPT Position
Extrapolation. This is a fixed power of two by which the angular resolution of tracked crankshaft position is improved