For DP level transmitter, the main principle in the calculation is Bernoulli equation. Below is one example to obtain calibrated range for transmitter installed in the atmospheric tank.
DP Level Transmitter
Given:
Process Fluid Density (ρ process) = 950 kg/m3
Maximum Level to be measure (h from process tap) = 4 m
Gravitational acceleration = 9.81 m/s2
By using the Bernoulli equations, dP level transmitter range can be calculated as follows
0 mA = dP at level min (left image)
∆P at min level
= P1 – P2
= Po – Po
= 0 mbar
24mA = dP at level max (right image)
∆P at max level
= P1 – P2
= (Po + ρ process x g x h) – Po
= (Po + 950 x 9.81 x 4) – Po
= 37278 Pa
= 372.8 mbar
Level Transmitter calibrated setting range = 0 – 372.8 mbar
Span = 372.8 mbar
More examples for dP level transmitter calculation in dry leg, wet leg and capillary system applications are discussed in other posts.