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Chapter 4 Troubleshooting & Repair Series 24-HP Instruction Manual
4-6 IM-24-HP
Troubleshooting the Flow Meter
Symptom: Output at no Flow
1. The low flow cutoff is set too low. At no flow, go to the
first column of the hidden diagnostics menu and record the Lvl
value. The low flow cutoff must be set above this value.
2. Example: at no flow , Lvl = 25. Set the low flow cutoff in the
Calibration Menu to approximately 28 and the meter will no
longer read a flow rate at no flow.
Symptom: Erratic Output
1. The flow rate may be too low, just at the cutoff of the meter
range, and the flow cycles above and below the cutoff making
an erratic output. The meter range is stamped on the label on
the outside of the electronics enclosure cover (based on appli-
cation conditions when the meter was ordered). Consult the
factory if necessary to confirm the meter range based on current
operating conditions. It may be possible to lower the low flow
cutoff to increase the meter range. See the example above for
output at no flow, only this time the low flow cutoff is set too
high. You can lower this value to increase the meter range as
long as you do not create the output at no flow condition previ-
ously described.
2. Mechanical installation may be incorrect. Verify the straight
run is adequate as described in Chapter 2. For in-line meters,
make sure the meter is not installed backwards and there are no
gaskets protruding into the flow stream. For insertion meters,
verify the insertion depth and flow direction.
3. The meter may be reacting to actual changes in the flow stream.
The output can be smoothed using a time constant. The dis-
played values can be smoothed using the time constant in the
Display Menu. The analog outputs can be smoothed using the
time constant in the Output Menu. A time constant of 1 will
result in the change in value reaching 63% of its final value in
one second. A time constant of 4 is 22%, 10 is 9.5% and 50 is
1.9% of the final value in one second. The time constant equa-
tion is shown below (TC = Time Constant).