This one of the more common forms of damage to a force sensor by a student.
What happens is that if the sensor gets hit hard, the strain gauge inside bends to one side and stays there (usually pushed in). If the sensor is working correctly the raw output voltage should about 2.5 volts when no force is applied. If this is not the case, the sensor typically works OK on the 50 N setting, but not on the 10 N setting.
Sensors in this state can sometimes be repaired by Vernier, but it depends on the extent of the damage. If you are in doubt, we recommend that you contact us for a Repair Authorization.
For the brave and electronics-savvy, it is possible to repair this yourself by adjusting the small recessed potentiometer offset screw on the right side of the sensor. Once you are on the calibrate screen of the software, adjust the potentiometer until the raw voltage output reads about 2.5 volts when no force is applied. Although this does not repair the bent strain gauge, it will shift the center reading and make it possible to use the sensor for both push and pull.
(Do not adjust the range setting on the left side of the sensor).