Emerson 475, User Manual

Page: 69 / 114

Fieldbus Functionality
4-17
RUNNING FIELDBUS
DIAGNOSTICS
The Fieldbus Diagnostics menu lets you run diagnostics to troubleshoot fieldbus
networks and devices. You can check the DC voltage, the noise level at low
frequencies, and the signal level and communication status. The selected tests are
automatically repeated and the test results are updated in the Diagnostics Results
window.
To view the values associated with the status indicators or the possible causes of the
values, run the diagnostic test, highlight the test on the Diagnostics Results window,
and tap
HELP .
DC Voltage Measurement
The DC voltage test displays the amount of DC voltage on a segment. The word Limit
appears if the DC voltage measurement is out of the -37 V to 37 V range. If the DC
voltage is out of this range, there may be a faulty terminator, wiring problem, or power
supply problem.
This test displays the measurement value, measurement unit, and one of the status
indicators listed below.
OK - The value is within the acceptable range.
High - The value is greater than 32 V.
Low - The value is less than 9 V.
Error - There is an error in the measurement or within the 475 Field Communicator.
Noise Level Measurement
The noise level test displays the amount of noise on the segment. The word Limit
appears if the noise level measurement is greater than 1.0 V. If the low frequency
noise is too high, the power supply or power conditioner may be faulty.
This test displays the measurement value, measurement unit, and one of the status
indicators listed below.
OK - The value is within the acceptable range.
High - The value is greater than 75mv from peak to peak.
Error - There is an error in the measurement or within the 475 Field Communicator.
Signal Level Measurement
The signal level test determines if a 475 Field Communicator can receive signals from
devices on a segment. To measure the fieldbus signal level, make sure an LAS is on
the segment. Up to 16 different nodes are checked. The word
Limit appears if the
signal level value is greater than 1.3 V. The word Low appears if the signal level value
is less than 100 mV.
This test displays the node address, measurement value, measurement unit, and one
of the status indicators listed below.
- All signal responses from the device were received by the 475 Field
Communicator.
! - One or more signal responses from the device was not received by the 475
Field Communicator. This may be caused by noise on the segment.
X - No signal responses from the device were received by the 475 Field
Communicator. This may be caused by noise on the segment.
Error - The measurement value is less than 75 mV or there is an error within the
475 Field Communicator.