BEKA BA314NG, Manual

Page: 9 / 41

4.2 Pulse input
The BA314NG can display speed and run-time from
sensors with a wide variety of pulse outputs located in
a Zone 2 hazardous areas or in a safe area. Fig 3
shows the connections when the sensor is located in
Zone 2 and Fig 4 the connections required when the
sensor is in a safe area.
Fig 3 Connections for sensor in Zone 2
Fig 4 Connections for sensor in safe area
Providing the BA314NG Tachometer is correctly
installed in Zone 2, the input terminals may be
connected to a certified sensor located in Zone 1 as
shown in Fig 5. The sensor should have Ex e or
Ex d certification permitting installation in Zone 1.
Intrinsically safe Ex i certified sensors should not be
used.
Fig 5 Connection to an Ex d or Ex e sensor in
Zone 1.
4.2.1 Input switching thresholds
For reliable operation the Tachometer pulse input
must fall below the lower threshold and rise above
the upper thresholds shown in the following table.
Input transducer
Switching thresholds
Lower Upper
Open collector

2k

10k
Voltage pulse low 1.0V 3.0V
Voltage pulse high 3.0V 10.0V
Magnetic pick-off 0mV 40mV peak
Proximity detector 1.2mA 2.1mA
Switch

100

1000
Sensors with a switch contact, proximity detector or
an open collector output require energising which is
achieved by linking Tachometer terminals 3 and 4.
4.2.2 Switch contact input
Any sensor with a mechanically or magnetically
activated switch contact located in Zone 2 or in the
safe area may be directly connected to the pulse
input terminals 5 and 6. The Tachometer input is
non incendive therefore the switch contacts do not
need additional protection in Zone 2. The switch
sensor and associated wiring should be able to
withstand a 500V rms insulation test to earth. Most
magnetically activated reed relays used in sensors
comply with these requirements. The BA314NG
contains a configurable debounce circuit to prevent
contact bounce being counted. See section 6.6.
9