The first thing you should do is make sure that the problem is not in the ULI. This can be done by swapping the ULI, cable, and power supply out one at a time. When you are sure that the ULI is fine, consider the following suggestions to determine what is wrong with the Motion Detector:

1. Make sure that you do not have something else, like a photogate, or a radiation monitor plugged into the DG1 or DG2 connectors on the ULI II.
2. look in the connector labelled Port2 and see if the little wires are parallel. If they are crossed, or crooked, try to straighten them out.
3. If neither of these suggestions help, contact Vernier Software to see about having the unit inspected.