101364 Model FT2
6. Troubleshooting
Caution! The electronics, sensor and sensor interconnect wires supplied by Fox are calibrated as a single
precision mass flowmeter. Interchanging sensors or sensor wiring will impair the accuracy of the flow meter.
If you experience any problem with your Model FT2 Flow Meter, call Fox’s Customer Service Department,
Technical Assistance at (831) 384-4300.
Problem Possible Cause Action
Unit will not power-up a) No power input
b) Bad fuse
c) Bad Power supply
a) Turn power on
b) Replace fuse. See section 5.5
c) Verify 24 VDC input power.
Velocity Measurement seems low a) Probe not oriented properly
b) Sensor dirty
a) Orient probe per Section 2.2.3
b) Clean sensor. (Refer to section 5.2,
Preventative Maintenance)
Velocity measurement is erratic
or fluctuating
a) Very turbulent flow
b) Sensor dirty
c) Sensor broken
d) Probe not mounted securely
e) Malfunction in flow meter
f) Verify Installation guidelines
(see Figure 2-4).
a) Adjust dampening per section 4.1.10
b) Clean sensor (refer to section 5.2)
c) Return flow meter to Fox for repair
(refer to section 6.2 for shipping
instruction)
d) Probe must be mounted securely
without vibration
e) Return flow meter to Fox for repair
(refer to section 6.2 for shipping
instruction)
f) Install meter accordingly to
guidelines.
The following is a summary listing of problems occasionally encountered with the FT2 Thermal Mass Flowmeter
and it’s installation.
1.
Inadequate power source.
For those models that are powered by 24VDC, a 24VDC ±1VDC, 25-watt power supply is
recommended. If the voltage supplied is not within this range or if the power supply is not rated
for 25 watts minimum, a variety of problems can occur including inaccurate flow readings, dim
display and faulty programming action. The input voltage must be within the range of 23 to 25
VDC as measured at the power input terminals of the flowmeter electronics.
2.
Improper wiring connections for power and/or 4-20mA output signal.
The FT2 requires a separate power source for the main board and the two 4-20mA output signals.
Two wires supply 24VDC power to the main board. Two wires are used for each of the 4-20 mA
output signals. Refer to Figure 3-2 and Figure 3-3.
3.
Improper 4-20mA wiring.
The FT2 flowmeter can have the 4-20mA signal connected in an “isolated configuration” or “non-
isolated configuration”. In the isolated configuration, the customers signal receiving equipment
(PLC, DCS, etc.) powers the 4-20 mA loop. Refer to Figure 3-3.
Fox Thermal Instruments Inc., 399 Reservation Road, Marina, CA 93933 Page 47
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