General / Accessories
Troubleshooting FOUNDATION Fieldbus with Fluke 190C Series ScopeMeter Application Note
A technical guide on using the Fluke 190C Series ScopeMeter to diagnose and troubleshoot FOUNDATION Fieldbus H-1 segments by analyzing Manchester encoding waveforms.
Table of contents
Quick guide from the manual
This application note provides procedures for using the Fluke 190C Series ScopeMeter to troubleshoot FOUNDATION Fieldbus H-1 segments. It focuses on identifying signal integrity issues, such as noise interference, random glitches, or faulty devices, by analyzing DC waveform characteristics.
Troubleshooting FOUNDATION Fieldbus H-1 Segment
To diagnose a segment, follow these steps:
- Connect the ScopeMeter probe and grounding lug across both wires of the H-1 segment. Note that the ScopeMeter is battery-operated and isolated from earth ground.
- Configure the scope to capture a 32-microsecond bit pattern.
- Set the voltage capability to capture 0.75 volts DC peak-to-peak.
- Observe the waveform. If 24-volt DC power is present and the Link Active Scheduler (LAS) is communicating, a waveform should appear. If no waveform appears, the LAS is likely faulty.
- Compare the observed waveform to the specified trapezoidal characteristic of Manchester encoding.
Isolating Faulty Devices
If the waveform appears degraded or contains inadvertent spikes, a field or host device on the segment may be misbehaving. To isolate the problematic device:
- Remove one device at a time from the segment.
- Monitor the waveform to see if the corruption disappears.
- Spikes in the waveform typically indicate a faulty communication card in the field device or at the host LAS.
Manufacturer information
Fluke Corporation
Practical help
Common problems
No waveform appears on the scope
Verify 24-volt DC power is present. If power is present but no waveform appears, the Link Active Scheduler (LAS) is likely faulty.
Degraded waveform or inadvertent spikes
This indicates a misbehaving field or host device. Remove devices one by one to isolate the source of the corruption.
Before use
- Ensure the ScopeMeter is battery-operated to maintain isolation from earth ground.
- Verify the H-1 segment is a two-wire digital network.
- Set the scope to capture a 32-microsecond bit pattern.
- Set the scope voltage capability to 0.75 volts DC peak-to-peak.
Specs in practice
- Manchester encoding
- The digital communication protocol used by FOUNDATION Fieldbus, characterized by a specific trapezoidal waveform.
- LAS (Link Active Scheduler)
- The device responsible for regulating communication parameters on the fieldbus segment.
Model compatibility
- The procedure is specifically designed for FOUNDATION Fieldbus H-1 segments.
- The Fluke 190C Series ScopeMeter is required for its ability to read Manchester encoding.
Manual page author
Emily Carter
User documentation editor
Prepares concise manual descriptions and highlights the most useful setup, operation, and maintenance information for readers.