Filter
Top Products
Reference Manual
00809-0100-4665, Rev AA
August 2010
6-7
Rosemount 8732
QUICK
TROUBLESHOOTING
Step 1: Wiring Errors The most common magmeter problem is wiring between the sensor and the
transmitter in remote mount installations. The signal wire and coil drive wire
must be twisted shielded cable: 20 AWG twisted shielded cable for the
electrodes and 14 AWG twisted shielded cable for the coils. Ensure that the
cable shield is connected at both ends of the electrode and coil drive cables.
Signal and coil drive wires must have their own cables. The single conduit that
houses both the signal and coil drive cables should not contain any other
wires. For more information on proper wiring practices, refer to “Transmitter to
Sensor Wiring” on page 2-11.
Step 2: Process Noise In some circumstances, process conditions rather than the magmeter can
cause the meter output to be unstable. Possible solutions for addressing a
noisy process situation are given below. When the output attains the desired
stability, no further steps are required.
Use the Auto Zero function to initialize the transmitter for use with the 37.5 Hz
coil drive mode only. Run this function only with the transmitter and sensor
installed in the process. The sensor must be filled with process fluid with zero
flow rate. Before running the auto zero function, be sure the coil drive mode is
set to 37.5 Hz.
Set the loop to manual if necessary and begin the auto zero procedure. The
transmitter completes the procedure automatically in about 90 seconds. A
symbol appears in the lower right-hand corner of the display to indicate that
the procedure is running.
1. Change the coil drive to 37.5 Hz. Complete the Auto Zero function, if
possible (see “Coil Drive Frequency” on page 4-13).
2. Turn on Digital Signal Processing (see “Signal Processing” on
page 4-25)
3. Increase the damping (see “Damping” on page 3-17).
If the preceding steps fail to resolve the process noise symptoms, consult
your Rosemount sales representative about using a high-signal magnetic
flowmeter system.
Step 3: Installed Sensor
Tests
If a problem with an installed sensor is identified, Table 6-5 can assist in
troubleshooting the sensor. Before performing any of the sensor tests,
disconnect or turn off power to the transmitter. To interpret the results, the
hazardous location certification for the sensor must be known. Applicable
codes for the Rosemount 8705 are N0, N5, and KD. Applicable codes for the
Rosemount 8707 are N0 and N5. Applicable codes for the Rosemount 8711
are N0, N5, E5, and KD. Always check the operation of test equipment before
each test.
If possible, take all readings from inside the sensor junction box. If the sensor
junction box is inaccessible, take measurements as close as possible.
Readings taken at the terminals of remote-mount transmitters that are more
than 100 feet away from the sensor may provide incorrect or inconclusive
information and should be avoided. A sensor circuit diagram is provided in
Figure 6-1 on page 6-9.