Onicon F-3500 - Troubleshooting Guide; Earth Connections and Electrical Noise

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F-3500 Insertion Electromagnetic Flow Meter Manual 02/18 - 0665-11 Page 27
4.4 TROUBLESHOOTING GUIDE
NOTE: Also refer to the START-UP AND COMMISSIONING GUIDE located on page 19.
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 ow 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).
• Conrm that the output signals are consistent with each other
(frequency vs. analog, etc).
• Conrm that the control system is programmed for correct ow 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 ow reading.
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 ow 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
ow rate, but no ow
rate is indicated on the
local display module or
Btu meter
• Verify that all wires from the ow 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
F-3500 electromagnetic ow meters are designed to detect microvolt signal levels at the
electrodes located on the sensor head. These signals are generated as conductive uids ow
through the magnetic eld generated by the meter. If enough random electrical noise is present
at the electrodes, it can interfere with the ow signal measurement. Care must be taken during
installation to minimize the effects of electrical noise on the ow meter.