Regarding temperature and pressure compensation
Thread Content
The temperature and pressure compensation formulas for ideal gases sometimes involve square roots while others do not; is this due to different types of flowmeters? Compensation requires the use of square roots for flowmeters that measure differential pressure using orifice plates, but it is not necessary for vortex flowmeters. I hope experts can provide an explanation
Thermal and pressure compensation is closely related to the relationship between signal and flow rate. Anything that uses throttling measurement requires taking a square root. If there is a linear relationship between the signal and the flow rate, then there is no need to take the square root.
This is related to flow meters; all differential pressure flow meters require square root calculation. The location where this square root operation is performed can be chosen to be done by the transmitter or by the DCS. If you do not want to include a square root in your compensation formula, then you can simply apply the square root operation to all the transmitters used with the differential pressure flow meters on site
This post was last edited by qugd on 2022-6-30 at 10:42. Before proceeding, it’s advisable to understand the basic principles behind flow measurement as well as the mathematical formulas used for it. In the case of measuring flow using the differential pressure method (which can be considered as measuring velocity), it can be intuitively understood as the potential energy lost due to pressure reduction being converted into kinetic energy of the fluid in motion. Simply put, ΔE = m*g*Δh = m*ΔV²/2; here, g*Δh represents the pressure loss, which is also known as the differential pressure ΔP. Therefore, ΔV = √(2*g*Δh) = √(2*ΔP). Is this easier to understand? For vortex flow meters, they actually operate on the principle of Karman vortices; the flow velocity of the fluid is determined by measuring the frequency of the series of vortices generated behind the vortex element, and there is no direct mathematical relationship with differential pressure.
Whether compensation is required depends on the standards and specifications followed by the flow meter selected. The calculation formulas in the corresponding standards and specifications determine whether temperature compensation is required. Check and you’ll know.
It’s related to flow meters; those of the differential pressure type require taking a square root. However, when performing compensation, it’s necessary to consider whether the square root operation was done on the gauge itself or in the DCS system.
For different types of flowmeters, the formulas for temperature and pressure compensation vary; for example, with ultrasonic flowmeters and orifice plate flowmeters, it is necessary to refer to the relevant standard specifications.