Flomec D-40, Инструкция по эксплуатации

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6 Installation
2.2.1 Instrument Cable Twisted pair low capacitance shielded instrument cable 7 x 0.3mm (0.5mm
²
) should
be used for electrical connection between the flowmeter and remote instrumentation, use Belden
®
number 9363
or similar. The cable drain or screen should be terminated on a DC COMMON or a specifically assigned shield
termination at the readout instrument end only in order to protect the transmitted signal from mutual inductive
interference. IMPORTANT, tape off & isolate the shield at the flowmeter end of the cable.
The cable should not be run in a common conduit or parallel with power and high inductive load carrying cables
as power surges may induce erroneous noise transients onto the transmitted pulse signal or cause damage to the
electronics. Run the cable in separate conduit or with other low energy instrument cables. The maximum
transmission distance is typically 1000m (3300 Ft).
2.2.2 Hazardous area wiring Intrinsically safe wiring including using the reed switch pulse output as simple
apparatus, wiring to an Intrinsically Safe Instrument must be undertaken in accordance with the rules, regulations
and requirements applying to the territory in which the meter is being installed. The meters should only be
connected by qualified staff, the qualified staff must have knowledge of protection classes, regulations &
provisions for the apparatus in hazardous areas.
If the flowmeter is fitted with an intrinsically safe instrument refer to the appropriate manual & I.S. supplement for
wiring of the instrument inputs and outputs.
.
2.3 Pulse Output selection for pulse meters - Two types of output are available on each meter; open
collector from Hall Effect sensors or reed switch contact, unless it is intrinsically safe in which case only the reed
switch pulse is available. Each output type is linearly proportional to volumetric flow and each pulse is
representative of an equal volume of liquid.
2.3.1 Hall Effect Sensor Pulse Output - The Hall Effect Sensor is a high resolution solid state 3 wire device
providing an un-sourced, open collector, NPN transistor output. The term “un-sourced” means that no voltage is
applied to the output from within the flowmeter, it must be pulled to a ‘high’ or ‘on’ state by between 5~24Vdc
supplied from an external source, typically the receiving instrument. Used only for the E Register (RT40)
2.3.2 Reed Switch Pulse Output -The reed switch output is a two wire normally open SPST voltage free
contact ideal for installations without power or for use in hazardous area locations when Intrinsically Safe (I.S.)
philosophy is adopted. Note: when using the reed switch output the liquid temperature must not change at a rate
greater than 10ºC per minute (50ºF per minute). In general the reed switch life will exceed 2 billion actuations
when switching less than 5Vdc @10mA as is the case when combined with the I Register (RT12) and E register
(RT40) instruments.
2.4 Meter Calibration Factor (K or scale Factor) Each flowmeter is individually calibrated and has the number
of pulses per unit volume (eg pulses per litre or pulses per US gallon) entered into the program of the instrument.
Please refer to relevant instrument manual for programming details. Nominal figures are shown in the
specification section of this manual. For more accurate metering we recommend using the calibrated K factor.
Calibration certification is available upon request from your distributor.