ATI Technologies SmartTachSmartTach, User Manual

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TROUBLESHOOTING
SmartTach Operating Manual Page 6-5
Erratic Analog Output Voltage
This indicates that there are major variations in measured speed. The
problem is most apparent during hard acceleration and is caused by
erratic ignition timing. This problem occurs mostly on distributor type
ignition systems.
Possible solutions include:
•
Move measurement source to one with higher resolution. A
single spark plug wire has the lowest resolution in the ignition
system. The coil wire or using the TachSensor on the coil power
feed may produce better results.
•
If the measurement source has more than 1 pulse per cam rev,
try increasing the value of parameter 9.
Example:
V6 engine with distributor ignition. Inductive pick-up on a spark-plug
wire. Parameters 2, 3 and 9 set to 1
0
0.5
1
1.5
2
2.5
3
3.5
Figure 6 - 1: Erratic Analog Output
V6 engine with distributor ignition. Inductive pick-up moved to coil
wire. Parameter 2 and 3 set to 1 and parameter 9 set to 2
0
0.5
1
1.5
2
2.5
3
Figure 6 - 2: Normal Analog Output