5
The specified operating temperature for the BA377E
is -40 to +70°C. At temperatures belo -20°C the
instrument ill continue to function, but the display
digits ill change more slo ly and the contrast ill
be reduced.
This allo s the BA377E to be installed in all gas
Zones and to be used ith most common industrial
gases except carbon disulphide and ethyl nitrite
hich have an ignition temperature of 95°C.
2.3 Special conditions for safe use
The ATEX certificate has an 'X' suffix indicating that
special conditions apply to prevent an electrostatic
charge developing on the outside of the instrument
enclosure.
WARNING
To avoid an electrostatic charge being
generated instru ent enclosure should
only be cleaned with a da p cloth.
2.4 Power supply
When installed in a hazardous area the BA377E
must be po ered via a certified Zener barrier or
galvanic isolator from a dc supply located in the safe
area, or from certified associated apparatus ith an
intrinsically safe output.
The input safety parameters of the BA377E po er
supply terminals 1 and 2 are:
Ui = 28V dc
Ii = 200mA dc
Pi = 0.84W
Any certified Zener barrier or galvanic isolator ith
output safety parameters equal to or less than these
limits may be used to po er the BA377E.
The maximum equivalent capacitance and
inductance bet een terminals 1 and 2 is:
Ci = 2nF
Li = 4µH
To determine the maximum permissible po er
supply cable parameters the above figures, hich
are small and may be ignored for many applications,
should be subtracted from the maximum permitted
parameters, Co and Lo, specified for the Zener
barrier or galvanic isolator po ering the BA377E.
2.5 Input ter inals
When configured as a Timer the BA377E is
controlled via a single input that may be configured
for use ith different types of sensor. The input is a
separate intrinsically safe circuit, although the
negative side is internally connected to the negative
side of the po er supply and the reset terminal RS2.
See Fig 9.
Some types of sensor that may be connected to the
BA377E input, such as a s itch contact or a 2- ire
proximity detector, require energising to determine
their state. For sensors requiring energising fitting
an external link bet een terminals 3 & 4 connects an
internal 7V, 6mA supply to the input. Energising is
not required hen the BA377E input is connected to
a voltage source.
Fitting an energising link changes the output safety
parameters of the BA377E input as sho n in the
follo ing table hich also sho s the types of sensor
requiring energising (link fitting).
Output safety
para eters of
input ter inals 5 & 6.
Type of input Link* Uo Io Po
S itch 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 (lo ) No 1.1V 0.5mA 0.2mW
Voltage input (high) No 1.1V 0.5mA 0.2mW
*Link terminals 3 and 4
2.5.1 Sensors that do not require energising
Sensors ith a voltage output do not require
energising, therefore terminals 3 & 4 should not be
linked. When not energised i.e. ithout a link the
BA377E input complies ith the requirements for
simple apparatus. For intrinsic safety purposes,
sources of energy ith output parameters less than
1.5V; 100mA and 25mW are considered to be simple
apparatus (Clause 5.7 of EN60079-11), hich allo s
them not to be considered or documented hen
assessing the safety of an intrinsically safe system,
thus simplifying loop assessment.
This allo s almost any voltage output sensor to be
directly connected to the BA377E 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 ith requirements for
simple apparatus.
b. The sensor and associated iring can
ithstand a 500V rms insulation test to earth.
c. The sensor is located in the same hazardous
area as the BA377E.