| Flowmeter
Series > Proces-Data A/S |
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FUNCTIONS |
- Automatic
zero point correction.
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Unidirectional or bi-directional flow.
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Volumetric measurement in m3, litres, U.S. gallons
etc.
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Temperature measurement using an external temperature
detector.
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Temperature compensated flow measurement.
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Pulse output to electronic counter, 0-1000 pulses
per second.
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Pulse output to electromechanical counter, 0-5 pulses
per second.
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Stop signal from internal pre-set counter.
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Current output, 4-20 mA (extended version).
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A display unit, PD 210, can be direct connected. The
PD 210 has the following features: accumulated volume,
batch pre selection, flow rate indication, etc.
- Communication
capability to central data processing (extended version).
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Fig.
1: Structure |
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| 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.
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. |
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The
Electronic Module
is micro-processor based and both controls the sequence
of measurement and output signal transmission.
The use of the micro-processor has enabled a compact design
to be achieved yet including many functions. The electronic
module is available in two versions, standard and extended.
The standard version has two pulse outputs and can be
directly connected to a display unit.
In the extended version, one of the pulse outputs can
be changed into analogue output, 4-20mA. Besides, it is
possible to connect the transmitter to a data network
for central processing.
The Terminal Box is completely separated from the electronic
module. Hence connections can be changed without disruption
to the electronics. All terminals in the terminal base
are clearly marked with both number and function. The
box is also equipped with 3 cable glands, PG 11. |
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| OPERATING
PRINCIPLES |
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meterhead consists of a metering pipe with 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 average velocity of flow and therefore
to the volume flowing. |
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| The
micro-processor in the transmitter controls the current
generator keeping the magnetic field constant. The voltage
of the electrodes is taken via an amplifier and signal
converter to the micro-processor which calculates the
liquid flow. |
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