National Instruments NI DIDS-2103, Руководство пользователя

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NI DIDS-2100 Series User Manual | © National Instruments | 119
EncZ signal may be inverted via the Digital Input Setup window to properly present a rising edge between the same
two crank rising edges, each and every engine cycle.
Research Engine Encoder Patterns:
Optical encoders are a common source of signals for this pattern type in research applications. A single optical
encoder will typically have three different outputs named A, B and Z. Signals A and B are quadrature encoded 90
degrees out of phase, while Z is a single reference pulse per 360 degrees rotation of the encoder shaft. Signal A
or B (not both, typically A) may be wired to the Crank digital input while signal Z must be wired to the EncZ digital
input. Encoders having pulse-counts of 360 to 3600 pulses per rotation are common for research engine control
applications, although any pulse count may be used. The EPT ENC function will then extrapolate this to an improved
resolution, depending on the EPT extrapolation level.
If the optical encoder is mounted to the crankshaft, then NumberOfCrankTeeth should be set to the encoder pulse-
count and Stroke should be set according to the engine type – 2-STROKE or 4-STROKE. If the engine is a 4-stroke,
then a cam phase signal must be present and logically gated ( EncZMask ) with the Z pulse, so that every other Z
pulse is allowed to pass through. The gating function is accomplished by setting the EncZMask button to EncZ
Masked
. The result will be that the EPT function will see two full rotations of crank pulses for every Z pulse. The
cam phase signal may be a complex pattern, as long as it provides a consistent TRUE state for one Z pulse and a
FALSE state for the next, repeating this pattern. The Cam offset and extension functions can be used to adjust the
cam phase signal in order to meet the proper masking requirement of the Z pulse.
If the engine is a 2-stroke, then the EncZMask button of the EPT tab should be set to EncZ Passed .
If the optical encoder is mounted to the camshaft, then NumberOfCrankTeeth should be set to the encoder pulse-
count divided by two, Stroke should set to 4-STROKE, and the EncZMask button should be set to EncZ Passed .
This setup will track 720 degrees.
With encoder patterns, position 0 and tooth 0 correspond to the rising edge of the first CrankSig tooth following the
rising edge of the EncZ input.