Ams trex™ Device Communicator

Related information
Troubleshooting Fieldbus Diagnostics
5.10
View help for a measurement
You can view help text that provides information about each measurement. Each cell on
the Details screen has help text that describes overview information or actions you can
take to help troubleshoot the measurement or problem, if a problem is detected.
Procedure
1. Connect to the FOUNDATION fieldbus device or segment.
2. On the 
Fieldbus Diagnostics Overview
screen, tap 
Details
.
3. Press and hold on a measurement value, or highlight a cell and tap the checkmark
button on the keypad.
A menu is displayed.
4. Tap
Help
The Help text is displayed.
User Guide 
Fieldbus Diagnostics application
September 2021
User Guide 
163

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Figure 5-7: Help example
5. Tap 
OK
to close the Help screen.
5.11
Noise spectrum
The noise spectrum gives you a real-time view of the different types of noise that were
detected on the fieldbus segment. Various conditions can cause different types of noise.
The spectrum displays the measurements grouped by low frequency, in-band, and high
frequency noise. The frequencies between 9 and 39 KHz make the fieldbus signal.
Note
Before taking a noise measurement, remove the AC adapter from the Trex unit, if it is
connected. This isolates the Trex unit from the local power grid.
Frequency
Frequency range
Typical measurement values
Low frequency
870 Hz - 9 KHz
Less than1000 mV (peak-to-peak)
In-band frequency
9 KHz - 39 KHz
Less than 75 mV (peak-to-peak)
High frequency
39 KHz - 100 KHz
Less than 150 mV (peak-to-peak)
The gray/shaded area at the top of the noise spectrum shows the values that would
exceed the maximum values set in the measurement criteria for the low-frequency, in-
band frequency, and high-frequency measurements. If the measurement is in the gray/
shaded area, the Fieldbus Diagnostics Overview screen shows a status of CHECK. If the
measurement is below the gray/shaded area, the displayed status is GOOD.
The noise spectrum shows the highest measurement in mV (peak-to-peak) outlined in
black. Tap 
Reset Peak
to clear the black outline and have it reset to the most recent
Fieldbus Diagnostics application
User Guide
September 2021
164
User Guide

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highest peak. For example, use 
Reset Peak
to clear a noise spike that was detected when
connecting the Trex unit or other hardware to the fieldbus segment.
The measurements on the spectrum are also color-coded to indicate if the status of the
measurement. The colors become darker as the measurement increases.
•
Green = GOOD
•
Yellow = CHECK
•
Orange = CHECK
Note
The spectrum measurement will fail if the noise amplitude exceeds 1.5 V (peak-to-peak). If
you see multiple high-amplitude noise peaks, look for an unattached wire that may cause
high noise and saturate the noise detection.