PD 340 Flow Transmitter

Introduction

The PD 340 flow transmitter is a precision meter for the volumetric measurement of liquids, which are electrically conducting.

The transmitter can be used in applications where a hygienic design is required. The rugged construction of the transmitter makes it suitable for installations where solid particles are in the liquids.

FEATURES

Constructed according to hygienic requirements (3-A approved)

Type tested according to OIML R 117 2CD.

Automatic zero point correction.

Unidirectional or bi-directional flow.

Volumetric measurement in m3, litres, U.S. gallons etc.

Temperature compensated flow measurement.

Temperature measurement.

Linearizing function

Pulse output to electronic counter, 0-1000 pulses per second.

Pulse output to electromechanical counter, 0-5 pulses per second.

Stop signal from internal pre-set counter.

Current output, 4-20 mA.

P-NET Fieldbus communication, IEC 61158 Type 4.

CONSTRUCTION

The PD 340 flow transmitter consists of three parts: Meterhead, electronic module, and terminal box. The electronic module and the terminal box are the same for all sizes of transmitters. On the largest version (C 102, 4”) the Meterhead and the electronics form one integrated unit.

The Meterhead consists of a stainless metering pipe with clamp liners. Two magnet coils are mounted external to the metering pipe. Inside the metering pipe two stainless electrodes are mounted. The measuring section is designed so that changes in flow profile do not affect meter accuracy. Hence the transmitter has a wide range of flow rates within its linear accuracy. Changes from laminar to turbulent flow do not affect the linear accuracy and changing viscocity has no effect on meter accuracy. The calibration of the rneterhead is carried out using a computer controlled calibration facility.

The Electronic Module is microprocessor based and controls both the sequence of measurement and output signal transmission.

The electronic module is available in either standard version or extended version.

The standard version has two pulse output signals and one logic input. The transmitter can also be directly connected to a display unit.

The extended version can be configured for two pulse outputs, exactly as with the standard version. Alternatively, one of the pulse output signals can be changed into an analog current output signal, 4-20 mA, or the separate pulse outputs can be transformed to a combined 3-phased output signal.

See the manual for further details.

On the extended version electronics it is possible to connect the transmitter to a P-NET Fieldbus (data communication network) for central data collection or control.

The Terminal Box is completely separated from the electronic module. Connections can therefore be changed without disruption to the electronics. All terminals within the terminal box are clearly marked with both number and function.

Operating principles

The meterhead 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.

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 microprocessor calculates the liquid flow.

P-NET Fieldbus Interface

The extended versions of the Flow Transmitter utilize a P-NET fieldbus communication interface. This enables the Flow Transmitter to be connected directly to P-NET. P-NET is a fieldbus network designed for process control and data-collection.

Through the P-NET it is possible to display and change all the internal data within the Flow Transmitter, for example using the PD 4000 Flowmeter-Display.

The P-NET interface may also be used for data collection, eg. from a PC or a controller.

Meter sizes

The PD 340 Flow Transmitters are available in 6 sizes:

Size:		Max flow:
C 25	(1”)	8 m3/h
C 38	(1½”)	20 m3/h
C 51	(2”)	40 m3/h
C 63	(2½”)	80 m3/h
C 76	(3”)	120 m3/h
C 102	(4”)	200 m3/h

Meter selection guidelines

	As a main rule, a Flow Transmitter with a pipe dimension equal to the rest of the piping system should be selected.
	Never exceed the maximum flow rate of the transmitter (see above).
	If optimum measurement accuracy is primary concern, the smallest possible transmitter should be chosen, still observing that the maximum flow rate must under no circumstances be exceeded.
	To further improve accuracy, especially on very low flow rates, the Linearizing function should be enabled.
	If the chosen metering section is smaller than the pipework in the installation, the connecting pieces should be tapered.

Use the following diagram to get a quick graphical overview:

Quick selection guide