BEKA BA317NE, Manual

Page: 33 / 40

9.5 Pulse output
The BA317NE can be supplied with a factory fitted
isolated pulse output for retransmitting pulses to other
instruments.
Note: Only one of the three output options can be
fitted to a BA317NE Tachometer.
The pulse output is an open collector with the
following parameters:
Ron = 60

+ 3V
Roff = 1M
I max = 10mA
To retransmit a pulse to another BA317NE
Tachometer or to a BEKA counter, the pulse output
terminals may be directly connected to the input
terminals of the second instrument as shown in
Fig 16, alternatively the second instrument may be
located in the safe area. The second Tachometer
should be configured for an open collector input.
Fig 16 Pulse retransmission to another BEKA 'E'
Ex nA instrument.
A voltage output pulse can be generated as shown in
Fig 17. The current flowing in the pulse output circuit,
which is defined by resistor R1, should be less than
10mA. With a 24V supply R1 should therefore be
2,200

or greater.
The output pulse may be a synchronous duplicate of
the input pulse for re-transmission applications, or the
frequency may be divided and the pulse width
defined.
The retransmitted RTx annunciator on the
instrument display shows the status of the
retransmitted pulse output. Annunciator activation
depends upon the setting of
5ource
in the pulse
output configuration menu.
5caled:
Annunciator activated each time pulse output
open collector is
on , i.e. Ron is less than
60 Ω + 3V.
direct:
Annunciator continuously activated
9.5.1 Ex nA certification
The optional pulse output is a separate opto-isolated
Ex nA circuit with the following input parameters:
Ui = 30V dc
Ii = 100mA
This allows the pulse output to be connected to any
dc circuit providing that in normal operation the
maximum supply voltage is not greater than 30V dc.
Providing that the BA317NE Tachometer is correctly
installed in a panel enclosure located in Zone 2
complying with the requirements for Ex n protection,
the pulse output may be used to transmit a pulse to
any suitably protected equipment, except intrinsically
safe equipment, located in Zone 1 or 2 of a
hazardous area, or to equipment located in a safe
area.
Fig 17 shows a BA317NE Tachometer mounted in
an Ex n panel enclosure located in Zone 2
retransmitting a pulse to the safe area. The current
pulse flows through R1 resulting in a voltage pulse
output with an amplitude of about 20V.
Fig 17 Generating voltage pulse in safe area
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