ONICON FB-3500 Series - Manual (Page 26)

11451 Belcher Road South, Largo, FL 33773 • USA • Tel +1 (727) 447-6140 • Fax (727) 442-5699 • [email protected]
FB-3500 Bi-Directional Insertion Electromagnetic Flow Meter Manual 05/14 - 0718-3
Page 26
4.4 TROUBLESHOOTING GUIDE
NOTE: Also refer to the START-UP AND COMMISSIONING GUIDE located on page 22.
REPORTED PROBLEM POSSIBLE SOLUTIONS
No signal • Verify that the meter is properly inserted into the pipe.
• Verify that the electronics enclosure is parallel with the pipe.
• Verify 24 V supply voltage.
• Verify correct wiring to control system (see wiring diagram).
• Verify that there is flow in the pipe.
• Verify that the meter earth cable is connected to earth.
• Check to see if the alarm contact closure output is closed (orange &
white wires). A closed contact could indicate either an empty pipe or
excessive electrical noise, possibly due to a poor earth ground.
• Low conductivity water (≤ 20 µsiemens) may activate the empty pipe
detector and/or increase the potential for electrical noise problems.
Reading is too high or
low • Verify pipe size. Contact ONICON if pipe size is different from
calibration tag.
• Verify that the meter is properly inserted into the pipe.
• Verify that the electronics enclosure is parallel with the pipe.
• Verify correct wiring to control system (see wiring diagram).
• Confirm that the output signals are consistent with each other
(frequency vs. analog, etc).
• Confirm that the control system is programmed for correct flow range or
scale factor.
• Verify that the meter earth cable is connected to earth. A poor earth
connection can lead to excessive noise that can affect the flow reading.
Flow direction
indicator does not
change state when flow
direction changes. • Meter will not switch at very low flow velocities. Confirm that flow
velocity exceeds 0.2 ft/sec.
• Check for open connections between each contact closure wire (orange /
black & white / black) and the control system input.
Analog signal seems
high or low and does
not correspond to
frequency output • Check for ground loop or offset voltage:
• Disconnect analog signal input from control system and measure analog
output directly from the flow meter. Reconnect signal input to control
system and measure the analog signals again. Any difference between
these readings indicates a potential ground loop or offset voltage. Please
contact ONICON for further assistance.
Control system displays
flow rate, but no flow
rate is indicated on the
local display module or
Btu meter • Verify that all wires from the flow meter are connected to the display
module or Btu meter.
• The frequency output wires (green and yellow) must be connected for
any ONICON display or Btu meter.
4.4.1 Earth Connections & Electrical Noise Reduction
Introduction
FB-3500 Electromagnetic Flow Meters are designed to detect microvolt signal levels at the
electrodes located on the sensor head. These signals are generated as conductive fluids
flow through the magnetic field generated by the meter. If enough random electrical noise
is present at the electrodes, it can interfere with the flow signal measurement. Care must
be taken during installation to minimize the effects of electrical noise on the flow meter.