Sierra InnovaMass 240i Series, Instruction Manual, Page: 60 / 115

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Solution 1: Check the Minimum Noise Level
.

The Minimum Noise Level may be set too low. This will allow false
flow signals caused by noise or vibration to be seen. The Minimum
Noise Level must be set above the level of this noise/vibration to cut it
out. To do this,
Autoset the value. With NO FLOW in the pipe,
perform an Autoset and the meter will sense the noise and vibration
present, and set the Minimum Noise
Level just above this.
Case III: Meter Shows Erratic Flow Output
Solution 1: Check the measured velocity.

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.
Solution 2: Check the installation.

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.
Solution 3: Check the Minimum Noise Level.

Check the Minimum Noise Level. It may be possible to lower the
value to increase the meter range. See case above. Again, lowering
the Minimum Noise Level will allow more noise/vibration into the
meter and the meter will eventually lose the true flow signal in this
noise.
Solution 4: Check the Output Averaging setting.

Check the Output Averaging setting. The meter may be reacting to
actual changes in the flow stream. The output can be smoothed using
averaging. The meter samples the flow every 1 second (1 Hz). This
value is fixed. The output will compute a rolling average of each
reading over the requested time span. For example 5 seconds will average the last 5
readings together.
Solution 5: Check f, fi, and Ck settings.

Check f, fi and Ck. The vortex coefficient Ck may be incorrectly set.
The Ck is a value in the equation used to determine if a frequency
represents a valid vortex signal given the fluid density and signal
amplitude. In practice, the Ck value controls the adaptive filter (fi)
setting. During flow, view the f and fi values. The fi value should be
approximately 10-20 % higher than the f value. This is a low pass filter, so all
frequencies below fi can be seen by the Vortex meter. You may need to adjust Ck to
filter out noise that has a higher frequency than the flow signal. See Ck Adjust
For a very noisy environment, the Minimum Noise Level setting can result
in cutting off low flow rates.