Knowledge Base

Problem

Users setting up automated trial control in EthoVision XT — such as triggering external stimuli (videos, pellet dispensers) based on zone entry or rotation counts — find that stimulus events trigger too early, too late, or reset incorrectly during the trial.

Details

EthoVision XT trial control uses a rule-and-sub-rule logic system with conditional checks evaluated at specific moments. Common issues include:
- A reset condition firing before a triggered event (e.g., a video) has finished playing, because no time delay was added between the trigger and the reset.
- A condition using '=' operator evaluated at the wrong moment if the variable is updated in multiple rule boxes.
- Uncertainty about exactly when a dispensing action fires relative to a count threshold (e.g., on the 10th rotation vs. after it).
Affects EthoVision XT 17 and later with PhenoTyper/PhenoCount/external device integrations.

Solution

General timing and reset guidance:
1. When a sub-rule triggers a time-limited event (e.g., a 15-second video clip), insert a time condition between the trigger action and any reset action. The time condition duration should equal the length of the event (e.g., 15 seconds) to prevent the reset from firing while the event is still active.
2. Avoid using the '=' operator for variable comparisons when the variable may be updated asynchronously in other rule boxes. Use '>=' instead (e.g., count >= 10) to ensure the condition is captured reliably regardless of when the condition box becomes active.

For PhenoCount pellet dispensing:
1. When using TTL mode with a rotation count threshold, the pellet dispenses after the Nth rotation is completed (i.e., when the count reaches the threshold value).
2. Confirm PhenoCount is set to TTL mode for hardware-triggered dispensing.

For latency measurement to a triggered event:
1. Use the Free Interval output format in EthoVision's results settings to measure the time from trial start (or a defined event) to the moment the sub-rule condition is met.
2. Contact Noldus Support with your trial control file if timing behavior remains unexpected after applying these steps.