PD340 - Operating principles
The meterhead of the PD 340 Flow Transmitter consists of a metering pipe and two magnetic coils.
When a current is applied to the coils a magnetic field is produced at right angles to the metering pipe.
With a conductive liquid flowing through the metering pipe an electrical voltage is induced and measured by two electrodes mounted in the metering pipe. This voltage is proportional to the average velocity of flow and therefore to the volume flowing.
The PD 340 Flow Transmitter utilizes a square measurement chamber. The shape of the measurement chamber significantly reduces the influence of viscosity, type of liquid, and flow profiles.
Practical tests with the PD 340 confirm that it is not necessary to recalibrate the meter when changing product, for instance from water to milk. This would normally be necessary when using mag meters with traditional round measuring chambers.
Ue = K x B x V x D
Ue = voltage across electrodes
K = system constant
B = magnetic field
V = average velocity
D = distance between electrodes
The microprocessor in the transmitter controls the current generator keeping the magnetic field constant. The voltage across the electrodes is amplified and converted to a digital value from which the micro-processor calculates the liquid flow.