DP Transmitter Calibration for Liquid Level Tank


#1

A DP transmitter must be calibrated to measure the level of a liquid in an open tank. The density of the liquid is 1000 kg/m3. The DP transmitter will be mounted one meter below the bottom of the tank.

The tank is full when the height of the liquid in the tank is 5 meter and it is empty when there is only liquid in the high pressure line connected to the DP transmitter.

Determine the necessary calibration specifications for an output signal of 4 to 20 mA.

DP Transmitter Calibration for Liquid Level Tank

Empty:

P1 = Patm + ρhg

= Patm + 1000×1×9.81

= Patm + 9810

∴P1 – P2 = 9810 Pa

Full:

P1 = Patm + ρhg

= Patm + 1000×6×9.81

= Patm + 58860

∴P1 – P2 = 58860 Pa

Calibration specification:

Output = 4 mA when input = 9810 Pa (empty condition)

Output = 20 mA when input = 58860 Pa (full condition)