BEKA BA364E, Руководство пользователя

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To adjust an alarm setpoint select
5P1
x or
5P2
x and
press
(
which will reveal the current setting. The
flashing digit of the setpoint may be adjusted using
the
&
or
*
push button and the
(
button to move
control to the next digit. When the required setpoint
has been entered, pressing
)
will return the display
to the
5P1
x or
5P2
x prompt from which the other
setpoint may be selected, or the instrument may be
returned to the display mode by pressing
)
again.
Note: Direct access to the alarm setpoints from the
display mode is only available when the
AC5P
menu is enabled - see section 10.3.13
10.4 4/20mA output
The BA364G Counter can be supplied with an
optional factory fitted galvanically isolated 4/20mA
output which may be configured to represent the rate
or total display.
10.4.1 Intrinsic safety
The 4/20mA output has been certified as a separate
galvanically
isolated intrinsically safe circuit
complying with the requirements for simple
apparatus. This allows terminals C1 and C3 to be
connected to any intrinsically safe circuit protected
by a certified Zener barrier or galvanic isolator
providing the output parameters do not exceed:
Uo = 28V dc
Io = 200mA
Po = 0.84W
The maximum equivalent internal capacitance and
inductance of the 4/20mA output is:
Ci = 2.2nF
Li = 4µH
To determine the maximum permissible cable
parameters, these figures should be subtracted from
the maximum cable capacitance and inductance
specified by the certificate for the Zener barrier or
galvanic isolator powering the 4/20mA output circuit.
10.4.2 System design
The BA364G Counter 4/20mA output is a passive
current sink i.e. not powered, but it is totally isolated
from all other Counter circuits. It is effectively a
2-wire 4/20mA transmitter requiring a minimum
supply of 10V with its current being controlled by the
BA364G Counter. Subject to complying with intrinsic
safety interconnection requirements, the terminals
C1 and C3 may be directly connected to another
instrument located in the same hazardous area
which will accept a 4/20mA transmitter input.
The
4/20mA current output may also be transferred to the
safe area via a galvanic isolator or Zener barriers.
Fig 18 shows how a 2-channel Zener barrier may be
used to transfer the 4/20mA current output into the
safe area, alternatively a galvanic isolator may be
used.
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