BEKA BA337E, Manual

Page: 39 / 61

10.4.1 Solid state output
Each alarm has a galvanically isolated single pole
solid state switch output as shown in Fig 13. 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 = less than 5

+ 0.7V
Roff = greater than 1M

Note:
Because of the series protection diode some
test meters may not detect a closed alarm
output.
Fig 13 Equivalent circuit of each alarm output
10.4.2 Intrinsic safety
Each alarm output is a separate galvanically isolated
intrinsically safe circuit with output safety parameters
complying with the requirements for
simple apparatus
.
This allows the alarm output terminals A1 & A2 and A3
& A4 to be connected to almost any intrinsically safe
circuit protected by a Zener barrier or galvanic isolator
providing the output parameters of the circuit do not
exceed:
Uo ≤ 28V dc
Io ≤ 200mA dc
Po ≤ 0.84W
The maximum equivalent capacitance and inductance
between each set of alarm terminals is:
Ci = 22nF
Li = 4µH
To determine the maximum permissible cable
parameters Ci should be subtracted from the
maximum permitted external capacitance Co specified
by the certificate for the intrinsically safe interface
powering the alarm circuit, such as the solenoid driver
and switch transfer galvanic isolators shown in Fig 14.
Fig 14 Typical alarm application
10.4.3 Configuration and adjustment
When a BA337E or BA338E is supplied with alarms
the configuration menu is extended as shown in
Fig 15. The alarm functions appear after
clr gtot
,
and each alarm may be configured to operate on the
rate or total display.
For simplicity Fig 15 only shows the configurable
functions on the rate option of alarm AL1, the total
options is identical except that total alarms do not
have hysteresis.
Alarm AL2 is identical to alarm
AL1.
The following table summarises each of the alarm
configuration functions and includes a cross
reference to more detailed information. Again only
the functions on alarm AL1 are listed.
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