Introduction to the target flow meters principles.
With the target meter a physical target is located directly in the fluid flow.
The deflection of the target and the force bar is measured in the instrument.
The force on the target can be expressed as
F = cd ρ v2 At / 2 (1)
F = force on the target (N)
cd = overall drag coefficient obtained from empirical data
ρ = density of fluid (kg/m3)
v = fluid velocity (m/s)
At = target area (m2)
Advantages with the Target Flow Meter
- Can be used for any type of liquid, gas, or steam cryogenics.
- There is no moving parts such as bearings, to wear out causing failures.
- High reliability where life tests have been made to 20,000,000 cycles.
- Can be used for any line size from 0.5 inches and up with any type of mounting.
- Range/fluid changes accomplished by simply changing targets
- Turndowns aprox.15:1
- Can accept bi-directional flow where signal polarity indicates direction.
- Several materials are available. Among them 303/304 SS, 316 SS, hastelloy and inconel.
Disadvantages with the Target Flow Meter
- Calibration must be verified in the field.