8
|
ni.com
|
NI 9752 User Manual
Figure 7.
Negative Tooth Trigger Wheel
Figure 8.
Correct Signal Polarity for VR Input Circuit
Figure 9.
Incorrect Signal Polarity for VR Input Circuit
Each VR sensor input requires a positive sensor connection and a negative sensor connection.
Connect a positive sensor input to one of the NI 9752 pins labeled VR1 and VR2. Connect the
negative sensor inputs to GND pins on the NI 9752. The polarity of the sensor connection to the
NI 9752 is critical. Connect the leads of the sensor so that the positive input of the VR circuit
receives the waveform shown in Figure 8. The waveform shown Figure 9 is incorrect, and the
VR circuit does not properly respond to this waveform. The rapid zero crossing of the VR signal
must be in the negative direction.
The physical center of each tooth or gap corresponds to a known angular position of the trigger
wheel. This physical center of the tooth or gap always corresponds to the rapid zero-crossing of
the generated voltage pulse.
