User's Manual

The 402A Stopwatch Control unit enables a 401A,420A or 490A series clock to be used both as a
multifunction stopwatch and a time-of-day clock with the display freely switchable between time-of-day and
stopwatch time. The time-of-day count may be synchronised to a wide variety of external time codes, impulses
and time signals.
Four switches control the stopwatch count, display selection and function programming of the control unit.
The operation of these switches is illustrated on the following pages.
The stopwatch function can be programmed to count:
• Up from zero - program function SA, selection 1.
• Down from a pre-programmed start-time to stop at zero - program function SA, selection 2.
• To count down and then up through zero - program function SA, selection 3. In this mode a minus
sign will appear in the left hand character position when the count is minus and the most significant
digit is zero.
• To continuously count down to zero with automatic re-start from a pre-programmed start time -
program function SA, selection 4.
The stopwatch can be programmed to operate:
• In a simple start-stop mode - program function SB, selection 1.
• With one of four programmed spilt actions to enable the time intervals between sequential events to
be timed incrementally or accumulatively. Please refer to pages 14 and 17 for further information. -
program function SB, selections 2 to 5.
The stopwatch display can be programmed to show:
• Minutes, seconds and one hundredth seconds (minutes and seconds for 420A series clocks) -
program function SC, selection 1.
• Hours, minutes and seconds (hours and minutes for 420A series clocks) - program function SC,
selection 2.
• Minutes, seconds and one hundredth seconds (minutes and seconds for 420A series clocks) unless
the hours count is one or more in which case the display automatically switches to show hours,
minutes and seconds (minutes and seconds for 420A series clocks) - program function SC,
selection 3.
The countdown start time can be programmed in hours, minutes and seconds (hours and minutes for 420A
clocks). The programmed time is held in non-volatile EEPROM and is automatically recalled whenever the
stopwatch is in a countdown mode and the `RESET’ switch is pressed or automatically when count option -4
- is selected.
An optional internal interface module (404.R) provides a normally open voltage-free relay contact pair, rated
at 24v 1A dc and programmable from one to three seconds contact closure duration in steps of 0.1 seconds,
which starts when the countdown reaches zero - program function SD, selections 0 (no contact closure) to 30
(3 seconds closure).
The 402A Stopwatch Control unit can also be used to remotely set the clock to time and date.
The 402A controller unit is connected to the 401A, 420A or 490A clock by means of the three metre long
three core cable provided. The interconnecting cable may be extended to ten metres length using a screened
cable. Please refer to page 24 and 28 for details of the connections to the clock.
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402A Stopwatch Controller - 1
Issue 2.2