Unit scaling
= 360
Clock Scaling
= 1500
The result is shown in the read
-
only “Scale result”: 240 mDegrees/Clock
pulse
E Clock shift: (TDC position)
This setting can be used to shift the position of the 0 degree indication on
screen automatically. For example, if the TDC signal is not at the exact 0
degree position but comes in at 36.1 degrees, set the “Clock shift” to 36.1.
Note
Once the TDC point has been established, all samples recorded prior to TDC
detection will be scaled backwards from this point.
F TDC enable
When this setting is enabled, GEN DAQ systems will use the External
Trigger input signal to automatically establish the 0 degree reference (TDC:
Top Dead Center) for rotational measurements.
G TDC delay
The TDC delay parameter can be used to skip some of the beginning TDC
signals, e.g. to avoid jitter TDC problems while starting engines.
Example: If this setting is set to 5, then the 0 degree position is linked to
the 5
th
occurrence of the TDC signal after start of recording in the GEN
DAQ system.
H Use qualifier
This setting can be used to separate the ignition cycle from the exhaust
cycle. Typically, the ignition and exhaust cycles are treated as a 720
-
degree rotation cycle together. For every 360
-
degree rotation, a TDC pulse
will be generated by the engine. For the GEN DAQ system to separate the
0
-
degree TDC pulse from the pulse appearing at 360 degrees, we need a
second signal, the TDC qualifier.
The TDC qualifier is implemented by using the alarm function of the GEN
DAQ analog channels driving the alarm output of the GEN DAQ mainframe.
The alarm status will be AND
-
ed with the external trigger input to produce
the proper TDC signal selection. No additional wiring is required other than
to measure the qualification signal of one of the analog channels.
To separate the ignition cycle from the exhaust cycle, we could measure
the cylinder pressure, e.g. on Channel 1. Set the alarm level of Channel 1
to be active above 10 PSI. Disable all other alarm settings for all other
channels in the system. Enable the Use Qualifier setting. If Channel 1
measures less than 10 PSI, the alarm output signal will disable the TDC
detection. As soon as the pressure exceeds 10 PSI, TDC detection is
enabled. If no TDC is detected before the pressure drops below 10 PSI
again, the TDC detection is disabled again.
GEN3t
894
I3995-3.1 en HBM: public
