Noise Spectrum - Emerson AMS Trex User Manual

Fieldbus Diagnostics application
5.
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
Low frequency
In-band frequency
High frequency
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.
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Figure 5-7: Help example
Tap OK to close the Help screen.
Frequency range
870 Hz - 9 KHz
9 KHz - 39 KHz
39 KHz - 100 KHz
Typical measurement values
Less than1000 mV (peak-to-peak)
Less than 75 mV (peak-to-peak)
Less than 150 mV (peak-to-peak)
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