BEKA BA374NG, Manual

Page: 32 / 53

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7. TIMER APPLICATION EXAMPLES
This section illustrates three applications for the
BA374NG when configured as a Timer.
7.1 Measuring the time that a contact is
closed.
In this example a BA374NG is required to display
the time that a Zone 2 hazardous area contact is
closed. The display is required in hours and minutes
within the hazardous area and is to be reset to zero
by a push button located in the same hazardous
area, not by the instrument front panel push buttons.
The operator is required to zero the grand total by
operating the
)
and
*
buttons simultaneously.
No security codes are required to protect access to
the configuration menu or to the grand total reset.
Figure 13 shows the wiring for the BA374NG when
powered by a single channel Zener barrier. This
example illustrates how the Timer may be started
and stopped by one input, the second input is not
used in this application.
Fig 13 Starting & stopping timer with one input
The required instrument configurations for this
example are shown below.
Function Display Setting
Access code
CodE 0000
Function
FunCtion ELAP5E
Input A
inPut-A ContACt
De-bounce Input A
dEbounCE dEFAuLt
Display 2
di5P-2 oFF
Start stop
5tAr5toP ControL 4
Units
unit5 12 : 00
Set time
5Et t 99 : 59
Direction of count
up or dn up
Local total reset
rE5E EnbL oFF
Local grand total reset
Clr Gtot on
7.2 Controlling an Ex nA solenoid valve
This example illustrates how a BA374NG Timer can
open an Ex nA solenoid valve for 5 minutes each
time the start button is operated. The operator
needs to pause the process without affecting the
total time that the valve is open. At the end of the
process the Timer is required to automatically reset
within 10 seconds ready for the next timing cycle to
be started.
For this application the BA374NG Timer requires
dual control outputs which are a factory fitted option
and should be specified when the instrument is
ordered.
Control output 1 is used to switch the Ex nA solenoid
valve, and control output 2 is wired to the Timer's
reset terminals to perform the automatic resetting at
the end of the timing cycle, see Fig 10.
The control outputs are configured so that control
output 1 is closed when the timer is in the
run
state
and control output 2 is closed when the Timer is in
the
done
state with a 5 second on delay. The
sequence of events is shown in Fig 14, and the
Timer's configuration is listed at the end of this
section.
This valve opening process is to be linked to other
processes on the plant, therefore the status output is
required to indicate when the 5 minute valve open
period has been completed and the Timer has
entered the
re5et
state ready for the next cycle to
be started.
When the start button is operated the Timer enters
the
run
state and control output 1 closes for 5
minutes which opens the solenoid valve. At the end
of the 5 minute period, the Timer automatically
moves from the
run
to the
done
states and control
output 1 opens which closes the solenoid valve.
Control output 2 is externally wired to the Timers
reset terminals. It is configured to close when the
Timer enters the
done
state and has been configured
with a 5 second on delay. Therefore 5 seconds
after the Timer enters the
done
state, control
output 2 closes and resets the Timer ready to start
another cycle when the start button is operated.
If at any time during the cycle the stop button is
operated, the Timer will enter the paused state
which will stop the process until the start button is
operated when it will resume from the place at which
it was paused.
In this example Local total reset
rE5Et . EnbL
is
on .
This enables the Timer to be reset when power is
first connected by operating the
*
and
&
push
buttons simultaneously for more than three seconds.