ATI Technologies SmartTachSmartTach, User Manual

Page: 45 / 110

PARAMETERS
SmartTach Operating Manual Page 4-15
21 - Trigger Input Polarity
Parameter Group:
TrgInp
Options:
Neg
- Falling Signal Edge Trigger
Pos
- Rising Signal Edge Trigger
Default:
Neg
- Falling Signal Edge Trigger
Purpose: This parameter is used to select the signal "edge" to be detected for
the Trigger Input. Falling Edge refers to the positive-to-negative
(high-to-low voltage) transition of the input signal. Rising Edge refers
to the negative-to-positive (low-to-high voltage) transition of the
input signal.
How to Set: The signal "edge" corresponding to the Input should be determined
beforehand. This information may be available from an engine
service manual, or actually measured with an oscilloscope. In
general, the faster/straighter the edge, the more accurate the
measurement.
When using a magnetic sensor (or other slow transition time type
signal - as opposed to a square wave), it is recommended that the
Falling Edge setting be used if possible. This is the edge normally
used by production engine control systems. When the input is a
square wave signal, either setting may be used and the accuracy
will not be affected.
Examples:
Signal examples and recommended settings
Use Rising Edge Use Falling Edge Either Edge
NOTE: When parameter 20 is set to TS1, this parameter will be set to
Auto and cannot be changed.