KROHNE VFM 3100 EN - Manual (Page 27)

• VFM 3100 Body Serial Number: Enter alphanumeric Serial Num-
ber from VFM 3100 tag.
NOTE: Although the VFM 3100 will operate properly without this in-
formation, it is convenient to enter it at this point.
• Reference K-Factor: Enter numeric value from VFM 3100 body tag
NOTE: It is not necessary to enter the units of the Reference
K-Factor. The units, i.e., US (pulses/ft
3 ) or Metric (pulses/liter), are
determined internally by the VFM 3100, based on the nominal size of
the VFM 3100 (contained in the Model Code) and the entered nume-
ric value of the Reference K-Factor.
3. Troubleshooting
3.1. General Troubleshooting
To maximize the usefulness of this chapter, read this General Trouble-
shooting section first. Then, follow the applicable procedural steps in
the order presented. Persons performing troubleshooting procedu-
res should be suitably trained and qualified for those procedures.
NOTE: If applicable, remove transmitter under test from multidrop
environment.
3.1.1. VFM 3100 Has Incorrect Output
Check the configuration. Be sure the VFM 3100 has been configured
correctly.
Incorrect 4 to 20 mA Output
• Be sure the upper range value is correct.
• Check that the correct flow units are specified.
• Check that the VFM 3100 is not in the multidrop mode by
verifying that the polling address is zero. In the multidrop mode
the mA output is fixed at a constant 4 mA.
• Check that the VFM 3100 is not in one of the application
default modes.
a. For liquid the default mode is water.
For many situations this may be adequate.
b. For steam the default is 125 psig saturated steam.
There may be significant error at other pressures.
c. For gas the default mode is 100 psig air. Other gases and other
conditions require the correct configuration for density and
base density.
Incorrect Digital Output
• Check that the correct flow units are specified.
• For custom flow units check that the conversion factor is
correct.
Refer to “Determining Special Measuring Units” on page 43
to calculate the conversion factor.
• Check to be sure that the VFM 3100 is not in one of the appli-
cation default modes.
Incorrect Pulse Output
• Verify that correct flow units are used. Check the pulse reso-
lution factor.
• The scaled pulse output can only be used with a receiver that
does not calculate period, such as a counter.
3.1.2. VFM 3100 Output Indicates Flow When There Is No Flow
In some installations, the VFM 3100 can indicate flow when the line is
shut down. This could be the effect of a leaking valve, sloshing fluid,
or noise sources such as pump-induced pipe vibration. To eliminate
these false signals, try the following:
NOTE: Remote mounted VFM 3100 with standard temperature ran-
ge sensors may have noisy signals if the slide switch on the preampli-
fier is in EXT position. Be sure the switch is in the correct position to
match the sensor.
• Be sure there is no flow.
• Be sure the noise rejection feature is set to ON.
• If damping is ON and set to greater than zero, the noise spikes
that exceed the low flow cut-in will appear as decaying signals
less than the low flow cut-in.
• Adjust the low flow cut-in level to produce zero output.
This level can be automatically set or manually adjusted via the
configurator.
• Check that transmitter and power supply are properly earthed
(grounded). This is particularly important for remote installations.
Refer to “Field Termination” on page 19 and “Interconnection
Wiring for Remote Electronics” on page 13.
• For remote VFM 3100, verify that signal cable has been properly
terminated.
3.1.3. VFM 3100 Output Indicates Higher Flow Rate with
Decreasing Flow
• Be sure the noise rejection feature is set to On.
• Adjust the low flow cut-in level to produce zero output.
This can be done with automatic or manual adjustment.
3.1.4. Fluctuating Output
• Verify that the signal conditioning feature is On.
• Fluctuations may be a true picture of the actual flow.
• A small offset of 1 to 2% with rapid fluctuations may be caused
by gaskets protruding into the flow stream.
3.2. No Output Troubleshooting
NOTE: VFM 3100 with extended temperature range sensors will
have reduced output if the slide switch on the preamplifier is in STD
position. Be sure the switch is in the correct position to match the
sensor.
• Be sure there is flow.
• Check the power supply. The voltage across the + and -
terminals must be between 12.5 and 42 volts dc.
a. If voltage is zero, check for blown fuse in power supply.
b. If voltage is low, but not zero, the VFM 3100 may be loading
the power supply. Remove the field terminal cover. Disconnect
the + and - leads and measure the voltage from the power
supply. If the voltage returns to normal, the circuit is good to
this point. Reconnect power to the + and - terminals.
c. Remove the electronic module compartment cover. Loosen
the mounting screws and remove the electronic module from
the housing. Measure the following voltages on the B-R-O-Y
terminal block. They should be:
Red to Yellow: +2.6 +0.2 Volts dc
Orange to Yellow: +2.6 +0.2 Volts dc
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