BEKA BA337E-SS, Manual

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3.4 Power supply
When installed in a hazardous area the BA337E-SS
should be powered from a certified Zener barrier,
galvanic isolator or associated apparatus with an
intrinsically safe voltage output.
The safety parameters of terminals 1 and 2 are:
Ui = 28V dc
Ii = 200mA dc
Pi = 0.84W
Uo = 0
Io = 0
Any certified Zener barrier, galvanic isolator or
associated apparatus with output safety parameters
equal to or less than these input parameters may be
used.
The maximum equivalent capacitance and inductance
between terminals 1 and 2 is:
Ci = 2nF
Li = 4µH
To determine the maximum permissible cable
parameters the above figures, which are small and
may be ignored in some applications, should be
subtracted from the maximum permitted cable
parameters specified for the Zener barrier, galvanic
isolator or associated apparatus powering the
BA337E-SS Rate Totaliser.
3.5 Pulse input terminals
The BA337E-SS Rate Totaliser has a single pair of
pulse input terminals 5 and 6 that may be configured
for use with different types of flowmeter sensor.
For flowmeters with sensors that require energising
to determine their state, such as switch contacts or a
2-wire proximity detector in a turbine flowmeter, an
external link between terminals 3 & 4 of the BA337E-
SS connects an internal 7V, 6mA supply to the input.
Energising is not required when the Rate Totaliser's
input is connected to a voltage pulse source.
Fitting an external link between terminals 3 & 4
changes the output safety parameters of the Rate
Totaliser input terminals 5 & 6 as shown in the
following table. This table also shows the types of
sensor requiring energising (link fitting).
Output safety parameters
Type of input Link 3 & 4 Uo Io Po
Switch contact Yes 10.5V 9.2mA 24mW
Proximity detector Yes 10.5V 9.2mA 24mW
Open collector Yes 10.5V 9.2mA 24mW
Magnetic pick-off No 1.1V 0.5mA 0.2mW
Voltage input (low) No 1.1V 0.5mA 0.2mW
Voltage input (high) No 1.1V 0.5mA 0.2mW
3.5.1 Flowmeter sensors that don't require
energising.
Flowmeters employing magnetic pick-offs or voltage
pulse sensors do not require energising, therefore
terminals 3 & 4 should not be linked. When not
energised i.e. without a link, the output parameters
of the pulse input terminals comply with the
requirements for
simple apparatus . For intrinsic
safety purposes, sources of energy with output
parameters less than 1.5V; 100mA and 25mW are
considered to be
simple apparatus (Clause 5.7 of
EN60079-11), which allows their output parameters
Uo, Io & Po to be ignored when assessing the safety
of an intrinsically safe system, thus simplifying loop
assessment and documentation.
Almost any flowmeter with a voltage pulse output
may be directly connected to the BA337E-SS input
in a hazardous area providing that:
a. The flowmeter is a certified intrinsically safe
device having output parameters equal to or
less than:
Uo ≤ 28V dc
Io ≤ 200mA dc
Po ≤ 0.84W
or complies with requirements for
simple apparatus.
b. The flowmeter and associated wiring can
withstand a 500V rms insulation test to earth.
c. The flowmeter is located in the same
hazardous area as the BA337E-SS.
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