if i set my mass flow cut off to 5g/s and live zero is 4.99 g/s when there is no fluid flow . does that mean the 4.99 g/s is error due to installation.
If it is so does it have impact on my performance if mass flow meter. Whats the error acceptable to maintain the manufacturer claimed performance of 0.1%
Hello Chandu,
Coriolis flowmeters are “vibrating element” instruments. Like all vibrating-element devices, there is a small amount of instability in the resonance of the sensing components. Therefore, as the flow rate approaches zero, the inherent instability of the instrument becomes an ever-increasing component of the measurement. In the interest of not relying on measurements made up of a significant amount of non-flow signal, it is necessary to stop trying to measure flow when the instability becomes a significant portion of the measurement. That is why there is a flow cutoff.
Other things can contribute to the zero offset, including installation problems, material stuck or built up in tubes, erosion and corrosion & etc.
Live zero allows you to see the total flow signal, including the zero instability. It is useful sometimes in diagnostics.
Adding flow cutoff in no way impacts the performance of the instrument. You may increase the flow cutoff to whatever level you wish that is below the lowest practical flow you want to measure.
Does this fully answer your question?
In reply to Wayne590:
It really depends on the normal flow rate of material through the meter. For a Coriolis type say 2000 g/s, the 5 g/s zero is pretty insignificant. If you're normally charging around 50 g/s and it's hovering around 5 g/s, you'll have around 10% error in your total w/o being aware of the issue. There should be a way to zero out the instrument by deadheading the flow with it being liquid full if it's a Coriolis type or at least see the "true" zero. The zero reference is important as to get the 0.1% accuracy.
Generally it's nice to see the raw flow signal unclamped as it'll tell you a lot on the stability of the meter/installation.