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Chapter 4 Troubleshooting & Repair Series 780S Instruction Manual
4-2 IM-78S-B
Problem Possible Cause Solution
Velocity measurement is
erratic or fluctuating
Very erratic or non-uniform flow Follow installation requirements shown
in Chapter 2
Moisture present in gas flow Install a water trap or filter upstream of
the flow meter sensor
Flow conditioning plates are not
upstream of the sensor
Correct flow meter orientation
Sensor component broken Return to factory for replacement
Malfunction in system
electronics
Return to factory for evaluation
Ground loop Check wiring, see Chapter 2
Velocity measurement
seems too high or low
Sensor assembly not aligned
correctly to flow
Correct alignment with the flow indicator
pointing downstream in the direction of
flow
Flow conditioning plates are not
upstream of the sensor
Correct flow meter orientation
No response to flow from
sensor assembly
No power Turn on power to the flow meter
Low flow cutoff setting too high Correct low flow cutoff programming
using the Smart Interface software.
Flow rate below meter’s minimum
flow rating
Contact factory for instructions
Flow has exceeded the maximum
range of the flow meter
Set the user full scale to equal the fac-
tory full scale
Reduce flow below the maximum range
shown on the meter’s nameplate or con-
tact the factory for re-calibration advice
Sensor failure Return to factory for evaluation
Printed circuit assembly defective Return to factory for evaluation