BEKA BA377E, Руководство пользователя

Страница: 10 / 62

10
3.1.7 Voltage input
Two voltage input ranges are independently
selectable in the BA377E Timer configuration menu,
VoLt5 L
and
VoLt5 H
. When configured for either of
the voltage ranges, the input terminals 5 & 6 comply
with the requirements for
simple apparatus . This
allows the input to be connected to any certified
intrinsically safe voltage source located within the
same hazardous area as the BA377E having output
parameters equal to or less than:
Uo ≤ 28V dc
Io ≤ 200mA dc
Po ≤ 0.84W
The BA377E Timer may therefore be directly
connected to and controlled by most certified
intrinsically safe high level voltage signals.
The maximum permitted cable parameters will be
defined by the intrinsic safety certification of the
voltage source less the BA377E input parameters
which are small and can often be ignored.
The BA377E contains a configurable debounce
circuit to prevent false triggering of the instrument.
Three levels of debounce protection are available.
See section 6.5.6.
3.1.8 Remote reset
Connecting the external reset terminals RS1 and
RS2 together will reset the BA377E when configured
as a Timer and synchronise the displayed time when
configured as a Clock. Remote resetting may be
accomplished by any mechanically operated switch
located in the same hazardous area as the
instrument providing the switch and the associated
wiring can withstand a 500V rms insulation test to
earth. No Zener barrier is required.
A BA377E may also be remotely reset from the safe
area. Any switch may be used but a Zener barrier
is required to transfer the contact closure into the
hazardous area which may be combined with the
supply barrier so that only one package is required.
A diode return barrier is not suitable for this
application. Fig 1 illustrates how a BA377E may be
reset from both the safe and the hazardous area.
Note: When used as a Timer the BA377E may also
be reset from the display mode by operating the
&
and
*
push buttons simultaneously for more
than two seconds. See 6.5.19
3.1.9 Control outputs (optional)
Each of the two factory fitted optional control outputs
is a galvanically isolated single pole solid state
switch as shown in Fig 3. 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

+ 0.7V
Roff > 1M

Note: Because of the series protection diode some
test meters may not detect a closed alarm output
Fig 3 Equivalent circuit of each control output
Each control output is a separate galvanically
isolated intrinsically safe circuit with output safety
parameters complying with the requirements for
simple apparatus . This allows the control output
terminals A1 & A2 and A3 & A4 to be connected to
almost any intrinsically safe circuit protected by a
Zener barrier having output parameters equal to or
less than:
Uo ≤ 28V
Io ≤ 200mA
Po ≤ 0.84W
The maximum equivalent capacitance and
inductance between each set of control output
terminals is:
Ci = 22nF
Li = 8µH
To determine the maximum permissible cable
parameters Ci and Li of the BA377E should be
subtracted from the maximum permitted external
capacitance Co and inductance Lo specified by the
certificate for the Zener barrier powering the circuit
as shown in Fig 4. The internal capacitance and
inductance of other devices in the loop, such as the
solenoid valve in Fig 4, should also be subtracted
from Co & Lo.