Concept diagram based on official documentation; not recorded equipment or database measurements.
Cognex trigger received, no image: distinguish Debounce from Trigger Delay first
The symptom: A PLC or sensor appears to issue a trigger, but the expected image is missing. Increasing acquisition delay is not necessarily the remedy. First, distinguish a signal that is not accepted as a valid trigger from an accepted trigger that has not yet initiated acquisition. This is a vendor-documentation-based diagnostic, not a claimed field repair.
Two controls, two different decisions
The official In-Sight Spreadsheet 26.2.1 Acquisition Panel explains that under Single Trigger, Debounce (ms) is how long a trigger signal must remain active to cause acquisition. Its stated setting range is 0–10 ms. In the same mode, Trigger Delay (ms) specifies how long the vision system waits between receiving an acquisition trigger and starting image acquisition, with a 0–10,000 ms setting range.
Consider a purely illustrative timeline:
- Hypothetical pulse A remains HIGH for less than the configured Debounce time. It may never count as an accepted trigger.
- Hypothetical pulse B satisfies Debounce. The configured Trigger Delay then controls when the associated acquisition starts.
- Neither waveform is recorded from a real PLC, oscilloscope or Cognex camera.
The key distinction: making Trigger Delay larger does not validate a pulse that fails Debounce.
A read-only troubleshooting sequence
| Check | What to inspect | Why |
|---|---|---|
| 1. Physical/source signal | Wiring, sensor output and PLC output characteristics | A program bit transition is not proof of a matching camera-input pulse |
| 2. Camera and firmware | Exact In-Sight model, software and Trigger Type | Options depend on model and mode |
| 3. Actual trigger path | Trigger Source selection and the expected field interface | Physical input, network, factory protocol and manual triggers are different |
| 4. Pulse width | Configured Debounce and genuinely observed HIGH duration | Separate insufficient pulse duration from later acquisition timing |
| 5. Acquisition stage | Trigger Delay, acquisition complete and inspection timing | Separate acceptance from execution |
| 6. Model-specific exceptions | Line Scan, Sequence mode and related settings | Similar names do not imply identical timing behavior |
A Line Scan exception worth checking
The vendor explicitly notes that Trigger Delay is not supported on Line Scan vision systems. Do not diagnose a missing control as defective merely because a tutorial shows the control on a different camera. Sequence-mode Capture Delay is likewise a different setting with different scope.
What this article does not establish
The manual establishes setting definitions and supported ranges, not the root cause of a specific production fault. This draft has no measured electrical pulse, camera event log, licensed on-device screenshot or field-validation record. To confirm the cause in a real line, a responsible engineer must inspect the current configuration and signal timing before any controlled changes. Do not alter a running production line based solely on this article.
Primary official source: Cognex In-Sight Spreadsheet 26.2.1 Acquisition Panel
This diagnostic flow follows published In-Sight documentation. No actual camera, PLC pulse width, or field timing waveform was measured for this example; verify the exact device and I/O model before making changes.