Fieldbus Diagnostics application

The Fieldbus Diagnostics application lets you run diagnostics to troubleshoot fieldbus segments and devices. It provides power and basic communications for verifying device operations on an isolated mini-segment. The application provides optional communications for identifying the device list. You can connect the Trex unit at various points along the fieldbus segment, so you can isolate the location of a problem.

The Fieldbus Diagnostics application can help you identify problems caused by loose wire connections, water or moisture in cables or terminal housings, improper grounding, or issues with fieldbus segment installations.

Note: The Fieldbus Diagnostics application can be used with the Device Communicator communication module or Device Communicator Plus communication module. However, the Trex unit cannot power a FOUNDATION fieldbus device with the Device Communicator communication module. The application also requires a fieldbus license.


The Fieldbus Diagnostics application lets you measure:

  • DC voltage: -34 to 34 volts
  • Noise: Low-frequency (870 Hz - 9 KHz), in-band frequency (9 KHz - 39 KHz), and high-frequency noise (39 KHz - 100 KHz)
  • Fieldbus signal level: 100 - 1200 mV (peak-to-peak)

Quick ad-hoc network tests to isolate issues

You can use the Trex unit to connect to various connection points on the fieldbus segment to isolate an issue. For example, if the device fails to power due to a low-voltage at its terminals, use the Fieldbus Diagnostics application to measure the voltage at all cable connection points between the power supply and the device. These measurements can help you identify the section of cable or junction box where the voltage drop occurs.

Long-term tests to catch sporadic issues

If a device has issues for only part of the day, you can take measurements over a period of time to capture the time/date the issue occurs. For example, if you notice sporadic increases in noise, you can take a measurement for multiple hours to determine when the issue is occurring. This can help you relate the noise with another event, such as a variable-frequency drive starting and stopping throughout the day.

Periodic tests to help you track your network and create trends

You can take measurements every few months to create an overall trend/report for the fieldbus segment. For example, you can create one set of measurements when a device is installed, and another set of measurements a year later for comparison. This can help you track any slow degradation of the fieldbus segment.

The Fieldbus Diagnostics application has a logging feature that lets you save one or more sets of measurements to a comma-separated values (.csv) log file. The files can then be transferred to a PC for further review and analysis in a spreadsheet program.