Flomec 490, Инструкция по эксплуатации, Страница: 10 / 20

9
Electrical connections
3.4 Instrument cable installation requirements
Use twisted multi-core low capacitance shielded instrument cable (22 AWG ~ 7x 0.3
stranded) for electrical connection between the Insertion Meter and the remote
instrumentation. The screen should be earthed at the readout instrument end only to protect
the transmitted signal from mutual inductive interference.
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. Run the cable in separate conduit or with other low energy
instrument cables.
3.5 Pulse output selection ( standard outputs )
The standard Insertion Meter has two independent pulse output signals that are linearly
proportional to volumetric flow rate. Pulse transmission can be up to 1000 metres (3300 ft ).
An optional intrinsically safe (I.S.) Reed Switch only output is available
(see page 7).
Voltage pulse
(pulse wire) output
A self-generating pulse output which produces a strong 1.5 volt voltage spike of
approximately 10 micro/second duration with no dependence on rotor speed.
Square Wave Pulse (Hall sensor) ( also applies to non-magnetic & QP Hall outputs )
An NPN open collector transistor pulse output produced by a solid state Hall Effect device.
This three wire device requires 5~24vdc and produces an NPN square wave output (20mA
max. sink), pulse width is 2~75 mSec. The Hall output requires a pull up resistor, these are
generally incorporated in most receiving instruments. For (QP) Quadrature pulse output refer
details page 10.
Reed Switch output
The Reed Switch has a fast response capable of frequencies in excess of 80hz. Receiving
instruments should have the ability to suppress reed switch bounce (0.01µf capacitor) and a 1
meg pull up resistor would be typical.
Yellow
Green
Screen
Yellow ( + )
Green ( - )
Screen
Screen
Red
Black
White
(5-24vdc supply )
signal output
( -0v ground )