How to Troubleshoot an Eddy Probe

An eddy probe is frequently used in the building and construction industry.

A non-contact measurement device with a quick response is often necessary to determine the general condition of process machinery. Although simple in its construction, the eddy current probe is relatively easy to install and can stand up to the sometimes harsh elements present in process and manufacturing environments. A range of eddy probes are available, but all function in a similar fashion and serve the same purpose: to provide precision for non-contact measuring tasks. Troubleshooting an eddy probe may require a bit of investigation.

Things You'll Need

• Filter

Instructions

1. Inspect the test surface of the eddy probe, which may show some visible wear and tear or damage. Look for frayed or damaged wires, and replace them if necessary.

2. Verify that the frequency of operation is within range of the eddy probe. If the frequency is too high, the balance coil and the probe coil likely are not of the same value. Lower the drive voltage of the probe to correct the problem.

3. Reposition the cable from where it intersects the connector or the probe frame to an area where it does not touch either one. If the cable on the eddy probe displays intermittent or interrupted operation -- working occasionally and not working other times -- replace it with a new one.

4. Examine the filter settings. If the signals appear small, distorted or dead, replace the filter. Use a high-pass filter for high settings and a low-pass filter to achieve an independent display speed.

Tips & Warnings

• Using Teflon tape on the face of the eddy probe will reduce wear to the device, as well as prevent contact that may produce noise.

• Inserting a piece of foam rubber or a small bit of a sponge between the coil and the inside surface of the hole on the eddy probe will help to limit the high noise-to-signal ratio.

• Cleaning the connector contacts will help the eddy probe to perform better. Use an electrical contact cleaner or silicon spray for this task.

References

• Olympus: Probe Types and Their Usage
• SKF: Eddy probe systems

Resources

• Lion Precision: Eddy-Current Sensor Probes
• STI: SKF Condition Monitoring Eddy Probe Systems