National Instruments NI DIDS-2103 User Manual page 116

signal width being equal to one crank tooth period; therefore, the extension function is required to extend it over the
appropriate gap.
N+1 Patterns
Pattern Description:
N+1 patterns have N evenly spaced teeth and a single additional tooth (Plus1), placed between two evenly spaced
teeth, on the crankshaft trigger wheel. There are two different sub-configurations within this pattern type, specified
by the Plus1Location button. An advanced Plus1 tooth must be positioned such that it is advanced from the midpoint
between two evenly spaced teeth. The amount of advance must be at least ¼ of the normal tooth spacing. A
retarded Plus1 tooth must be positioned such that it is retarded from the midpoint between two evenly spaced teeth.
The amount of retard must be at least ¼ of the normal tooth spacing. N is stated in terms of evenly spaced teeth, as
if there were no additional teeth. For example, a 6+1 pattern would consist of 6 physical evenly spaced teeth and an
additional physical tooth placed between two evenly spaced teeth. EPT N+1 function can be configured to track 360
or 720 degrees depending upon an optional camshaft input. When tracking 360 degrees for 2-stroke engines, the
camshaft input is ignored. This is designated by configuring the function with Stroke = 2-STROKE. When tracking
720 degrees for 4-stroke engines, the camshaft input signal must be TRUE during every other Plus1 tooth. This is
designated by configuring the function with Stroke = 4-STROKE.
2-Stroke Applications (Stroke = FALSE):
For advanced Plus1 tooth configurations, position 0 and tooth 0 coincide with the first tooth following the Plus1
tooth. For retarded Plus1 tooth configurations, position 0 and tooth 0 coincide with the second tooth following
the Plus1 tooth. The CamSig input is ignored. CrankCount will increment from 0 to NumberOfCrankTeeth - 1.
CrankCount will not be incremented at the location of the Plus1 tooth. For example, if the Plus1 tooth is advanced,
and NumberOfCrankTeeth = 6, then CrankCount would increment from 0 to 5, such that tooth 5 would correspond
to the tooth immediately before the Plus1 tooth and tooth 0 would correspond to the tooth immediately following the
Plus1 tooth. As another example, if the Plus1 tooth is retarded, and NumberOfCrankTeeth = 6, then CrankCount
would increment from 0 to 5, such that tooth 5 would correspond to the tooth immediately after the Plus1 tooth and
tooth 0 would correspond to the second tooth following the Plus1 tooth.
4-Stroke Applications (Stroke = TRUE):
For advanced Plus1 tooth configurations, position 0 and tooth 0 coincides with the first tooth following the
Plus1 tooth while the CamSig input is TRUE. For retarded Plus1 tooth configurations, position 0 and tooth
0 coincide with the second tooth following the Plus1 tooth while the CamSig input is TRUE. The CamSig is
actually only used for achieving initial sync. Once sync is achieved, it is maintained according to the location of
each Plus1 tooth. However, CamSig is still monitored to report whether the signal is normally alternating high
and low at each Plus1 tooth. The CamHistory indicator of the EPT tab reports whether the signal is "Normal",
"Always High", "Always Low", or an unexpected pattern reported as "Error". CrankCount will increment from 0 to
2*NumberOfCrankTeeth - 1. CrankCount will not increment at the Plus1 tooth. For example, if the Plus1 tooth is
advanced, and NumberOfCrankTeeth = 6, then CrankCount would increment from 0 to 11, such that tooth 5 and
tooth 11 would correspond to the tooth immediately before the Plus1 tooth while CamSig is FALSE and CamSig is
TRUE, respectively. Tooth 6 and tooth 0 would correspond to the tooth immediately following the Plus1 tooth while
CamSig is FALSE and CamSig is TRUE, respectively.
Tooth numbering for the two different Plus1 tooth location configurations is shown in figures 4.6.c and 4.6.d below.
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