Citizen B51 User manual

A
C
B

3
2
English
CONTENTS
1. Features .................................................................................................. 4
2. Explanation of Displays and Buttons ................................................... 5
3. Setting the Time and Date .................................................................... 6
4. Characteristic Functions of Solar-Powered Watches ......................... 8
5. General Reference for Charging Times ............................................. 10
6. Charging Procedure ............................................................................ 11
A. Charging by Exposing the Solar Cell to Light ................................. 11
B. Charging by Swinging the Watch ..................................................... 13
7. Warning Features ................................................................................ 15
8. Using the Chronograph ....................................................................... 17
9. Zeroing the Chronograph Second Hand ........................................... 19
10. Helpful Hints in Using your Watch .................................................. 21
11. Secondary Battery ............................................................................. 22
12. Using the Tachymeter (When Provided) ......................................... 23
13. Precautions ......................................................................................... 24
14. Specifications ..................................................................................... 30
Make Sure the Watch is Sufficiently Charged Before Use
Check that the second hand of the watch is moving correctly in 1-second interval
movement before use. If the second hand is moving in 2-second interval move-
ment or is stopped, this indicates that the watch is not fully charged. When this
happens, expose the solar cell to light to recharge or recharge the watch by swing-
ing.
When exposing the watch to light, do not place the watch too close to the light
source. This can cause the watch to overheat which can lead to a possible mal-
function.

5
4
2. Explanation of Displays and Buttons
Please refer to the illustration of the watch on the inside cover.
Name Time display
Hour display
Minute display
Second display
24 hour display
Setting the time and date
Chronograph display
Chronograph second (1/5
second) display
1: Hour hand
2: Minute hand
3: Second hand
4: 24 hour hand
5: Chronograph second hand
6: Chronograph minute hand
A: Button
B: Button
C: Crown
Chronograph minute display
Start/stop
Reset
A
B
1. Features
This analog quartz watch incorporates a solar cell in the watch face. In addition to being
equipped with a photoelectric power generation function that converts light energy to
electrical energy, it also is equipped with a self-winding power generation function that
converts "movement of the watch" produced by swinging the watch while wearing on
the wrist into electrical energy. Once fully charged, the watch will continue to run for
approximately 5 months without recharging. In addition, this watch is also provided
with a chronograph function (60 minute clock) that allows measurement of time in 0.2
second (1/5 second) units.
This watch also uses a secondary battery for storing the electrical energy that is gener-
ated. This battery is completely free of mercury and other hazardous substances. Since
this secondary battery is able to be repeatedly charged and discharged, it is not required
to be periodically replaced as in the case of ordinary watch batteries.

7
6
<Setting the Time>
(1)Pull the crown out to the time correction position (2nd position) so that the second
hand stops at the 0 second position.
(2)Turn the crown to set the time.
*The date changes at 12:00 AM. Set the time while being careful not to mistake AM
and PM.
(3)Push the crown in to the normal position in synchronization with a telephone time
service or other official time service.
<Setting the Date>
(1)Pull the crown out to the date correction position (1st position).
(2)Turn the crown to set the date.
Turning the crown towards you (counter-clockwise) advances the date by one day.
The date will not move if the crown is turned in the opposite direction (clockwise).
(3)Return the crown to the normal position.
*Do not attempt to set the date between the hours of 9:00 PM and 1:00 AM. Setting
the date during this time may not result in the date changing on the following day.
* If the crown is of the screw-tightened type, set the time and date after first loosening
the screw. Retighten the screw after the time and date have been set.
3. Setting the Time and Date
If the watch stops or the second hand moves at two second intervals when setting
the time, charge the watch by referring to Section 6 entitled, “Charging Procedure”
to return the watch to the normal 1-second interval movement before attempting to
set the time and date.
7
60
45
30
15
24
20
16
12
8
4
Hours
24 hour hand
Seconds
Minutes
Date correction (1st) position
Crown
Time correction (2nd) position
Normal position

9
8
45
30
7
60
50
40
30
20
10
60
45
30
15
24
20
16
12
8
4
[Time Setting Warning Feature]
When the time is set
while undercharged
Irregular 2-second
interval movement
When the watch is
charged either by
exposing to light or
swinging, the quick
start function is
activated causing the
hands of the watch to
start moving
Watch stops
4. Characteristic Functions of Solar-Powered Watches
When the watch becomes undercharged, the warning feature illustrated below is acti-
vated and the display of the watch (movement of the second hand) changes.
[Normal Time Display]
7
60
50
40
30
20
10
60
45
30
15
24
20
16
12
8
4
When undercharged
When charged
1-second interval movement
When fully charged and the time is set
45
30
[Insufficient Charge Warning Feature]
7
60
50
40
30
20
10
60
45
30
15
24
20
16
12
8
4
45
30
2-second interval
movement
When undercharging is allowed to continue

11
10
If the second hand of the watch is moving in 2-second interval movement or has stopped
due to undercharging, recharge the watch either by exposing the solar cell to light or by
swinging.
A. Charging by Exposing the Solar Cell to Light
* Expose the surface of the solar cell to a fluorescent lamp, incandescent light or sunlight
to recharge.
* If the watch is ordinarily concealed from the light as a result of wearing long sleeve
shirts and so on, the watch will be susceptible to becoming undercharged as a result of
not being exposed to light. Try to place the watch in as bright a location as possible
when it is not worn.
* When there are few opportunities for exposing the watch to light, the watch can also be
recharged by swinging in the manner described below.
[Precautions When Charging by Exposing to Light]
* Avoid charging the watch at high temperatures (approx. 60°C/140°F and above) since
allowing the watch to become overheated during charging can lead to a malfunction.
6. Charging Procedure
5. General Reference for Charging Times
(Case of Charging by Illuminating Solar Cell Only)
Charging times differ depending on the watch model (type of face, etc.). The charging
times shown in the table below are meant to only serve as a rough indicator of required
charging times.
*The charging
time indicated
refers to the
duration of
continuous
illumination.
Luminance
(Lux) Environment
Charging time
Charging
time for 1 day
of operation
Charging time from
stop until 1-second
interval movement
Full
charging
time
Typical office
Under a fluorescent
lamp (30 W) at a
distance of 60-70 cm
(24-28in.)
Under a fluorescent lamp
(30 W) at a distance of
20 cm(8 in.)
Cloudy day
Under direct sunlight
on a summer day
2 hours
45 minutes
15 minutes
4 minutes
2 minutes
37 hours, 30 minutes
15 hours
5 hours
1 hour, 30 minutes
30 minutes
335 hours
143 hours
45 hours
13 hours
2 hours, 30
minutes
Full charging time: Time from the state in which the watch is stopped until it is fully charged
Charging time for 1 day of operation: Time required for the watch to run for 1 day using the
normal time display (1-second interval movement)
500
1,000
3,000
10,000
100,000

13
12
B. Charging by Swinging the Watch
When there are few opportunities for charging the watch by exposing to light, occasion-
ally charge the watch by swinging. In addition, for those persons who only wear the
watch for short periods of time (several days) or when there is little movement while
wearing the watch, it is also recommended to charge the watch by swinging.
Swing the watch back and forth over a dis-
tance of about 20-25 cm (8-10 in.) at the rate
of about 2-2.5 strokes per second.
* Swing the watch for about 300-500 times
(strokes) when it has stopped.
<How to Effectively Charge the Watch by Swinging>
Examples:
* Charging in close proximity to an incandescent lamp or halogen lamp which can
easily reach high temperatures.
* Charging in locations that can reach high temperatures such as on an automobile
dashboard.
* When charging with an incandescent lamp, always make sure to keep the watch at least
50 cm (20 in.) away from the lamp to prevent the watch from overheating.

15
14
7. Warning Features
When this watch becomes undercharged, a warning feature is activated and the display
of the watch changes.
2-second interval
movement
<Insufficient Charging Warning Feature>
When the second hand is moving in 2 second intervals (moving once every 2 seconds),
this means that the watch is undercharged. Although the watch will continue to run
normally at this time, the watch will stop if 2-second interval movement is allowed to
continue for roughly 1 day. When this happens, charge the watch by referring to Sec-
tion 6 entitled, “Charging Procedure” so that it returns to normal 1-second interval
movement. Furthermore, the chronograph function cannot be
used when the insufficient charging warning feature has been
activated (during 2-second interval movement).
* If charging is only performed until the watch returns to 1-sec-
ond interval movement, it will again return to 2-second inter-
val movement within a few minutes. It is therefore recom-
mended to additionally charge the watch for at least one day’s
worth of charging by exposing to light or by swinging (200-
300 times) to ensure continuous operation.
45
30
* Charging will not proceed efficiently if the watch is swung too fast or too slow.
* When swinging the watch, although the sound of the generator turning can be
heard from inside, this is normal and does not indicate a malfunction.
* The watch should be swung approximately 200-300 times to ensure 1 full day’s
worth of charging when running normally (1-second interval movement).
* Charging can be performed even more efficiently by combining charging by ex-
posing the watch to light and charging by swinging.
* Since this watch is provided with an overcharging prevention feature, there is no
risk of damage to the watch due to excess charging.

17
16
8. Using the Chronograph
This chronograph is able to measure and display time in 0.2 second (1/5 second) units up
to a maximum of 59 minutes and 59 seconds. After completing measuring time for 60
minutes, it returns to the reset display and stops.
[Chronograph Reset Display]
60
50
40
30
20
10
60
50
40
30
20
10
* If the chronograph second hand
does not return to the zero second
position when the chronograph has
been reset, correct the second hand
position by referring to Section 9
entitled, "Zeroing the Chronograph
Second Hand".
Chronograph seconds
Chronograph
minutes
<Time Setting Warning Feature>
After the watch has been recharged after having stopped due to being undercharged,
although the watch hands will begin to move, the time will not be correct. The second
hand will begin irregular 2-second interval movement (moving irregularly once every 2
seconds) at this time indicating that the time is incorrect. Reset the time after suffi-
ciently charging the watch by referring to Section 6 entitled, "Charging Procedure”.
When the time has been reset, the second hand will no longer move irregularly in two
second intervals, and return to either 1-second or 2-second interval movement. In the
case of 2-second interval movement, the watch must be additionally charged.
Irregular 2-second
interval movement
45
30

19
18
9. Zeroing the Chronograph Second Hand
The zero position of the chronograph second hand may rarely shift out of position after
replacing the battery or after the watch has been subjected to a strong shock. When the
chronograph second hand does not return to the zero position when the chronograph has
been reset, correct the hand position using the following procedure.
60
50
40
30
20
10
Chronograph second hand Chronograph minute hand
Normal position
Crown
Correcting position
(2nd position)
A
B
<Measuring Time with the Chronograph>
(1) Pressing button starts and stops the chronograph.
(2) Pressing button when the chronograph is stopped returns the chronograph to the
reset display.
* If button is pressed by mistake during chronograph measurement, the chronograph
will return to the reset display. Be careful not to accidentally press button during
time measurement.
B
A
B
B
Reset Measurement Stop Reset
Can be repeated
A A
B
A