Keyence XG / CV-X — Trigger Input but No Image Capture

Keyence · beginner · 20 min

When a Keyence XG or CV-X vision system receives a trigger but doesn't capture, the cause is usually the flowchart structure or a waiting state — not the camera. Check the program flow first.

ℹ️ On XG/CV-X the flowchart is the program. A trigger only captures if execution actually reaches the capture unit — most 'no capture' cases are a flow that never gets there.

Trigger comes in, but nothing captures

On a Keyence XG or CV-X vision system, the program is a flowchart of units executed in order. A capture only happens when execution reaches the capture unit. Per Keyence's own troubleshooting FAQ, the usual causes are:

  1. The capture unit isn't under the start unit. If the capture unit is not placed within the executed branch below the start unit, the trigger never reaches it and no image is taken.
  2. An execution-waiting unit sits above the capture unit. If a unit above the capture — such as a terminal/execution-waiting unit — has not been executed, flow stalls before the capture. Check whether the flowchart is stuck waiting.

Trigger fires but the monitor image doesn't update

A related symptom: the trigger is accepted but the on-screen image never refreshes. On XG/CV-X the displayed image updates when the flowchart reaches the end unit. If the process stopped partway through the flowchart, the image stays frozen.

  • Check whether %WaitReady is ON — that indicates the flowchart is in a waiting status and hasn't completed the pass. Resolve whatever the flow is waiting on so it reaches the end unit and updates the image.

Camera-setting changes that don't take effect

Another common trap: changing camera settings on the controller and seeing no effect. By default, camera settings can only be adjusted with the capture unit in the XG VisionEditor — changes made to camera settings on the controller are not applied. To allow controller-side camera changes, select [Use system settings] on the [Capture Opt.] tab of the capture unit.

Step-by-step checks

  1. Open the flowchart in XG VisionEditor / CV-X and confirm the capture unit is placed under the start unit in the executed branch.
  2. Look for a stalled unit above the capture — an execution-waiting or terminal unit that hasn't run. Confirm its condition is met.
  3. Check %WaitReady — if ON, the flow is waiting; clear the wait so execution reaches the end unit.
  4. Verify the trigger source/mode matches how the line fires the system, and confirm the trigger signal is actually arriving at the input.
  5. If camera settings won't apply, enable [Use system settings] on the capture unit's [Capture Opt.] tab.

When it's really hardware

Only after the flowchart structure, waiting state, and trigger wiring check out should you suspect the camera, cable, or lighting. Trigger a single manual capture to confirm the optics before replacing hardware.

Key points

  • A trigger only captures if execution reaches the capture unit — confirm it sits under the start unit in the run branch.
  • An execution-waiting/terminal unit above the capture can stall the flow before it captures.
  • The monitor image updates only when the flowchart reaches the end unit; %WaitReady ON means the flow is waiting.
  • Controller-side camera changes don't apply unless [Use system settings] is enabled on the capture unit's [Capture Opt.] tab.
  • Verify the trigger source/mode and signal before suspecting the camera, cable, or lighting.

Codes and symptoms

No capture on trigger — Trigger accepted, no image
Flow never reaches the capture unit — capture not under start, or a waiting unit above it stalls execution.
%WaitReady = ON — Flowchart waiting
The flowchart is in a waiting state and hasn't reached the end unit, so the displayed image doesn't update.