BEKA BA368C, Manual

Page: 8 / 93

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1.9 ACCESSORIES
1.9.1 Scale card
The BA368C has a window on the right hand side
of the display to hold a card showing the units of
measurements e.g. Litres, seconds, rpm.
Instruments can be supplied with a printed scale
card showing any units specified at the time of
ordering. If a printed card is not requested, a blank
card will be supplied.
Scale cards can easily be marked on-site as
follows:
a. Remove the rear terminal block(s) and the
rear panel as shown in Fig 1.4
b. Carefully pull the instrument assembly from
the enclosure.
c. Gently pull and then slide the blank scale
card towards the display window until the
card is free. Mark the card with the required
legend and replace in the slot.
d. Reassemble the instrument.
1.9.2 Tag number
The BA338C can be supplied with a thermally
printed tag number on the rear panel. This tag
number is not visible from the front of the
instrument after installation.
1.9.3 Optional control outputs / alarm outputs
The BA368C can be supplied with two
programmable solid state single pole outputs. The
function of these outputs depends upon how the
BA368C has been programmed i.e. as a counter,
timer, tachometer or a clock. Full programming
information is contained in each section of this
manual
WARNING
These control outputs should not be
used for critical safety applications such
as an emergency shut down system.
When the BA368C power supply is
turned off or disconnected, both control
outputs will open irrespective of how
they have been programmed.
Annunciators on the instrument display indicate the
status of both control outputs.
1.9.3.1 Solid state output
Each output is a galvanically isolated single pole
solid state switch as shown in Fig 1.5. The outputs
are polarised and current will only flow in one
direction. Terminals A1 and A3 should be
connected to the positive side of the supply.
Ron = 5
Ω
+ 0.6V
Roff = greater than 180k
Note: Because of the series protection diode
some test meters may not detect a closed
control output.
Fig 1.5 Equivalent circuit of each control output
1.9.3.2 Intrinsic safety
Both control outputs comply with the requirements
for
simple apparatus specified in Clause 5.5 of
EN50020:1994. This allows them to be connected
to any intrinsically safe circuit protected by a
certified Zener barrier or galvanic isolator providing
that the output parameters of each circuit do not
exceed:
Uo = 28Vc
Io = 200mA dc
Po = 0.85W
No system certificate has been issued for the
BA368C switch contact outputs, as the system
certificate for the circuit to which the alarms are
connected remains valid.
The maximum equivalent capacitance and
inductance of each BA368C control output is:
Ci = 40nF
Li = 30µH
To determine the maximum permissible cable
parameters, the equivalent output parameters
must be subtracted from the maximum cable
capacitance and inductance specified by the
system certificate of the circuit connected to each
control output.