About Rosemount vortex flowmeters
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One of the Rosemount integrated vortex flowmeters in this unit has a measurement range of 0–100 cubic meters per hour; the medium used is compressed air. When it is not in use, its reading occasionally fluctuates from zero to around forty or fifty. 1. On-site inspection revealed that the signal strength was very low, at just a little over 1 unit; occasionally it would rise above 4, indicating unstable signal quality ； 2. Using automatic optimization doesn’t help either; however, after optimization the small-signal cutoff value automatically jumps to around 63. Once the small-signal cutoff is adjusted to a reasonable level, the value shown is around 15, with fluctuations between 15 and 18. At this point the valve is in the closed position (the valve has some internal leakage; it was checked but the leakage seems not to be that severe). 3. After restoring the filter to its factory settings, I manually reduced the low-pass cutoff frequency (I decreased it by several levels until the signal returned to near zero; only then did it match the frequency roughly. Increasing the frequency didn’t produce any changes. I’m not sure if this approach is correct). After that, the signal value was around 4, and the flow rate indicated a value between 0 and 0.6. However, even after closing the valve once the flow rate exceeded this level, the value didn’t return to zero, remaining around 1–2. Could the experts familiar with Rosemont please advise on how to handle this? Was there something that wasn’t checked properly? I haven’t checked the probe yet as time was short; it’s only been a few months, so I think there shouldn’t be any problems. Thank you all first
Please check first whether this flow meter is vibrating. If it is vibrating, that will have an impact
There was slight seismic activity, but it seems the impact shouldn’t be that significant
Then try increasing the trigger level value and see
Please take the time to check whether there is any AC signal in the 24V circuit
Is this watch installed properly? Are both the upstream and downstream straight sections meeting the requirements? Is the flow rate sufficient? Is the density ratio setting in line with the operating conditions? Should a gas be chosen as the measuring medium?
If conditions permit, take the table offline and place it in a vibration-free location to check; it’s likely still due to vibration
I didn’t dare adjust the trigger level – does that have a big impact? Is 4 the default for all?
None of these are a problem; they’ve been working fine all along
If it’s allowed, I’ll take it apart and take a look when the time comes.
There’s no need to disassemble it; compressed air has a low density, and since its sensor’s sensitivity is set high, it becomes very sensitive to vibrations as well. It’s a typical zero-point instability issue; only low-flow cutoff can be applied – change it in his settings.