BEKA BA377E-SS, Manual

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2.5.1 Sensors that do not require energising
Sensors with a voltage output do not require
energising, therefore terminals 3 & 4 should not be
linked. When not energised i.e. without a link the
BA377E-SS input complies 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
them not to be considered or documented when
assessing the safety of an intrinsically safe system,
thus simplifying loop assessment.
This allows almost any voltage output sensor to be
directly connected to the BA377E-SS input in a
hazardous area providing that:
a. The sensor 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 sensor and associated wiring can
withstand a 500V rms insulation test to earth.
c. The sensor is located in the same hazardous
area as the BA377E-SS.
The BA377E-SS EC-Type Examination Certificate
specifies that the equivalent capacitance and
inductance of the BA377E-SS sensor input is:
Ci = 2nF
Li = 4µH
To determine the maximum permissible cable
parameters these figures should be subtracted from
the maximum permitted output parameters Lo and
Co specified by the certificate for the sensor
connected to the BA377E-SS input terminals. The
BA377E-SS input parameters are small and
therefore unlikely to make a significant difference to
the allowable cable parameters.
2.5.2 Sensors that require energising
Switch contacts, proximity detectors and open
collector sensors require energising which is
achieved by linking two BA377E-SS terminals
together as described in section 2.5. When
energised, the output parameters of the BA377E-SS
input are:
Uo = 10.5V dc
Io = 8.2mA dc
Po = 25mW
These parameters do not comply with the
requirements for
simple apparatus and should be
considered when assessing the safety of the sensor
connected to a BA377E-SS input.
Any certified intrinsically safe sensor may be
connected to the BA377E-SS energised input
providing that the sensor's input safety parameters
are equal to, or greater than, the output safety
parameters of the BA377E-SS input shown above.
This is not restrictive and most intrinsically safe
sensors will comply. A sensor complying with the
requirements for
simple apparatus , such as a
mechanically operated switch contact, may also be
connected.
This allows most mechanically operated switches,
open collector transistors and certified intrinsically
safe NAMUR proximity detectors to be directly
connected to the BA377E-SS energised input. The
sensor and wiring should be able to withstand a
500V rms insulation test to earth and the sensor
should be located in the same hazardous area as the
BA377E-SS.
The BA377E-SS EC-Type Examination Certificate
specifies that the maximum capacitance and
inductance that may be safely connected to the
energised input (link connected) is:
Co = 2.4µF
Lo = 200mH
Again this is not restrictive as the combined
capacitance and inductance of most sensors and
connecting cable will be less than this.