# Possible Causes of ERR Statistics

The vision sensor returns ERR for an image when an error occurs during the image acquisition. Monitoring View counts the number of ERR images for the active program. The following errors increase the ERR statistics:

Problem | Description
Untrained App | Occurs when you have not trained the app yet.
Missing Fixture | Occurs when you have trained a fixture but it cannot be found within the image.
Region of Interest Outside Image | Occurs when you have trained a fixture and it is found in the image, but the resulting Region of Interest is partially or fully outside the image.
Acquisition Trigger Overrun | Occurs when the vision sensor is triggered while it is busy with a previous image acquisition. This typically happens when the vision sensor is triggered faster than it can acquire.
Acquisition Buffer Overflow | Occurs when the image acquisition is successful, but the vision sensor cannot process the image. This typically happens when the vision sensor captures images faster than it can process them.