Rosemount 8712, Reference Manual

Page: 138 / 212

Reference Manual
00809-0100-4664, Rev BA
January 2010
Rosemount 8712
C-6
High Process Noise
Parameters
The High Process Noise diagnostic has two read-only parameters. It does not
have any configurable parameters. This diagnostic requires that flow be
present in the pipe and the velocity be > 1 ft/s.
5 Hz Signal to Noise Ratio
Reads the current value of the signal to noise ratio at the coil drive frequency
of 5 Hz. This is a read-only value. This number is a measure of the signal
strength at 5 Hz relative to the amount of process noise. If the transmitter is
operating in 5 Hz mode, and the signal to noise ratio remains below 25 for one
minute, then the High Process Noise diagnostic alert will activate.
37 Hz Signal to Noise Ratio
Reads the current value of the signal to noise ratio at the coil drive frequency
of 37 Hz. This is a read-only value. This number is a measure of the signal
strength at 37 Hz relative to the amount of process noise. If the transmitter is
operating in 37 Hz mode, and the signal to noise ratio remains below 25 for
one minute, then the High Process Noise diagnostic alert will activate.
Troubleshooting High
Process Noise
The transmitter detected high levels of process noise. If the signal to noise
ratio is less than 25 while operating in 5 Hz mode, proceed with the following
steps:
1. Increase transmitter coil drive frequency to 37 Hz (refer to “Coil Drive
Frequency” on page 4-16) and, if possible, perform Auto Zero
function (refer to “Auto Zero” on page 4-15).
2. Verify sensor is electrically connected to the process with grounding
electrode, grounding rings with grounding straps, or lining protector
with grounding straps.
3. If possible, redirect chemical additions downstream of the magmeter.
4. Verify process fluid conductivity is above 10 microsiemens/cm.
HART Fast Keys 1, 2, 4, 4
LOI Key XMTR INFO
AMS Tab Diagnostics
HART Fast Keys 1, 2, 4, 5
LOI Key XMTR INFO
AMS Tab Diagnostics