Erratic and drifting Fz and Tx values on 311-001 Force/Torque Sensor

Description

We have installed a new NXB-SNS-311-001 sensor on the wrist of our R-50 robot for a new automated deburring cell. The sensor is powered with a stable 24VDC supply and is recognized by the robot controller on the EtherCAT network. However, the data we are receiving is unusable. Specifically, the force readings in the Z-axis (Fz) and torque readings around the X-axis (Tx) are extremely noisy and drift by as much as 100N over a few minutes, even when the robot is completely stationary and unloaded. We have re-seated the EtherCAT and power connectors, verified the cable shielding is properly grounded at the controller end, and power-cycled the entire system multiple times with no improvement. We suspect the sensor may have a faulty strain gauge or internal electronics. We are also seeing an intermittent communication error on the controller teach pendant. Our project is on hold until we can get stable force feedback.

Symptoms

• Force/Torque data drifts significantly when robot is stationary.
• Readings for Fz and Tx axes are noisy and jump unpredictably.
• Controller logs intermittent EtherCAT communication error E-4511 (Slave Data Invalid).
• Sensor status LED flickers occasionally between green and amber.

Resolution

The investigation determined the root cause was not a hardware fault with the NXB-SNS-311-001 sensor, but an EtherCAT network configuration issue within the robot controller. The controller's EtherCAT master was configured with a very fast cycle time and an overly restrictive Distributed Clocks (DC) sync window. This configuration did not provide enough tolerance for the high-resolution data transmission from the sensor, causing intermittent synchronization loss. This loss manifested as data jitter, drift, and the E-4511 error code. By adjusting the DC Sync0 cycle time and widening the monitoring window for this specific slave device, stable communication was established. After the change, the sensor data was stable, accurate, and within the advertised specifications.

Resolution Steps

1. Connect to the robot controller's engineering software.
2. Navigate to the EtherCAT Master configuration tree.
3. Select the NXB-SNS-311-001 sensor slave device.
4. Open the 'Advanced Settings' tab and locate the 'Distributed Clocks (DC)' parameters.
5. Change the 'Sync0 Cycle Time Multiplier' from 1 to 2.
6. Increase the 'Sync Window Monitoring' value to 150% of the base cycle time.
7. Save the updated configuration to the controller.
8. Perform a cold restart of the robot controller to apply the new network settings.
9. Monitor the live sensor data to confirm that drift and noise have been eliminated.