OMRON G9SX Security Unit Configuration and Troubleshooting

Typical scenario: A device has two hazardous areas. Zone 1 is protected by a safety light curtain, while Zone 2 is protected by a safety door. The equipment can only operate at full speed when the light curtain is unobstructed and the safety door is closed. By connecting logical AND gates, this "double conditional confirmation" can be easily achieved.

Input configuration and cross fault detection

The safety input of the G9SX unit supports 1-channel or 2-channel connections and has the ability to detect cross faults, which is crucial for meeting ISO 13849-1 Cat. 2/3/4.

Dual channel input (2-channel):

Used to connect safety door switches or emergency stop buttons with Direct Opening Mechanism. T11/T12 and T21/T22 must receive the ON signal simultaneously for the safety output to turn ON.

When the Y1 terminal is open circuited, the cross fault detection function is enabled. The system will continuously monitor whether there is a short circuit between T11 and T12, and between T21 and T22. Once detected, the safety output will be immediately locked and the ERR indicator light will be lit.

When the Y1 terminal is connected to+24V, the cross fault detection function is disabled. This mode is suitable for connecting safety sensors with self diagnostic output pulses (such as safety light curtains, laser scanners), as the outputs of these sensors themselves contain test pulses and cannot conflict with internal cross detection.

Single channel input (1-channel):

Only connect T11/T12, keep T21/T22 open circuit. At this point, Y1 must be connected to+24V to disable cross detection. Suitable for simple circuits that do not require Cat.4.

Reset mode and feedback monitoring

The correct configuration of reset logic is the key to preventing accidental restarts. G9SX defines reset behavior through terminals T31, T32, and T33.

Auto Reset:

Wiring: T32 short circuited to+24V.

Behavior: When all safety input conditions are met, the safety output automatically turns ON immediately, without the need for manual intervention. Suitable for remote control or hazardous areas that are not frequently accessed.

Manual Reset:

Wiring: T33 short circuited to+24V.

Behavior: After all safety input conditions are met, an external reset signal is required: T31 must go from ON ->OFF ->ON (i.e. press and release a reset button). This is the most commonly used mode, which requires the operator to confirm that the danger has been resolved before restarting.

Feedback loop: T31 terminal is usually used to connect auxiliary normally closed contacts of external contactors (such as KM1, KM2). When the safety output drives the contactor to disconnect, its auxiliary contacts close and send the signal back to T31. If the feedback detected by T31 does not match expectations when the safety output is turned on (such as contact welding adhesion), G9SX will detect the fault and lock the output to prevent restarting in a dangerous state.

Fault diagnosis: LED status codes and solutions

The G9SX series is equipped with detailed LED indicator lights, which are the first-hand tool for on-site troubleshooting. Understanding the flashing patterns of these indicator lights can quickly pinpoint the root cause of the problem.

LED status fault description Possible causes Checkpoints and countermeasures

ERR flashing

Other lights do not light up, internal circuit or electromagnetic interference fault 1. Strong electromagnetic interference

2. Internal circuit damage 1. Check on-site grounding and anti-interference measures

2. Replace the unit

ERR is constantly on

T1/T2/T6/T7 flashing safety input channel fault 1. Input wiring error or disconnection

2. Cross fault detection configuration error

3. Input device contact adhesion 1. Check T11/T12 or T21/T22 wiring

2. Check the Y1/Y2 wiring (open circuit is enabled,+24V is disabled)

3. Check the safety switch or sensor

ERR is constantly on

FB flashing feedback/reset input fault 1. External contactor auxiliary contact feedback incorrect

2. T31/T32/T33 wiring error

3. Expansion unit connection issue 1. Check if the NC contacts of the contactor are open and closed normally

2. Confirm the automatic/manual reset wiring

3. Check the expansion unit cables and terminal connectors

ERR is constantly on

EI flashing instantaneous safety output fault 1. Safety output (S14/S22) short circuit or overload

2. Logical AND gate output (L1) wiring fault

3. The ambient temperature is too high. 1. Check the output load (whether the current exceeds 0.8A)

2. Check the wiring between L1 and downstream T41/T42

3. Check unit spacing and ventilation

ERR is constantly on

ED flashing power-off delay output fault 1. S44/S54 output overload or short circuit

2. The OFF delay dip switch settings on the front and rear panels are inconsistent. 1. Check the load current

2. Confirm that the positions of the front and rear dip switches are exactly the same

ERR is constantly on

AND flashing logic and AND input fault 1. T41/T42 wiring length exceeds 100 meters

2. Logic and gate signal branches exceed 4 units

3. The AND switch at the receiving end is not set to "AND". 1. Shorten the wiring length or use shielded cables