Casio GW-M5610U

The Casio GW-M5610U (also called GW-M5610U-1) is a digital G-Shock watch that charges using sunlight and keeps precise time by syncing with atomic clock radio calibration signals.

Search

I like attending work meetings on time and started looking for a wristwatch that could maintain precision in time. To my surprise, I discovered that all digital/quartz wristwatches deviate by a few seconds within a month. Mechanical watches are worse (even million dollar ones) - deviate by seconds within a day!

The only precise solutions turned out to be smart watches (that sync with NTP servers over the internet) or digital watches that sync to the atomic clock radio signals that are transmitted on most continents. Needless to say that I preferred the radio sync - anything to avoid the complexity of smartwatches and their poor battery performance. I asked the friendly folks on WatchCrunch for a recommendation and the answer was GW-M5610.

I went to order the GW-M5610 (usually named GW-M5610-1 on sites) and found that it had been recently updated to GW-M5610U with an updated module and other features. And that is how I ended up with this gem.

Features

• G-Shock Protection: Watch has triple 10 resistance - 10+ year battery life, 10+ bar water resistance and surive fall of up to 10 meters.
• Multiband 6: Casio’s branding for the atomic clock radio sync feature. It can sync with any of the 6 such radio sources on the planet (see below).
• Tough Solar: Casio’s branding for the solar charging technology used in their G-Shock watches.
• Water resist 20 BAR: Water resistance up to 200 meters. Essentially the watch can be used in all water scenarios except scuba diving.
• Module 3495: This is the module used in this watch and this is the search term to use to obtain the user manual online.
• Time Signals: The watch supports these 6 signals:
  • Japan Time Calibration Signal (JJY) transmitted from 2 locations: Fukushima and Fukuoka at 40 kHz/60 kHz.
  • Chinese Time Calibration Signal (BPC) transmitted from Shangqiu at 68.5 kHz.
  • US Time Calibration Signal (WWVB) transmitted from Fort Collins at 60 kHz.
  • UK Time Calibration Signal (MSF) transmitted from Anthorn at 60 kHz.
  • German Time Calibration Signal (DCF77) transmitted from Mainflingen at 77.5 kHz.

Buttons

The user guide calls the 4 buttons A-D, but I will be referring to them using their position on the watch since that is unambiguously easier:

• A: Top left (TL)
• B: Top right (TR)
• C: Bottom left (BL)
• D: Bottom right (BR)

Operation

• Switching modes: Keep pressing BL repeatedly to switch between the following modes:

  • Timekeeping
  • World time
  • Alarm
  • Stopwatch
  • Timer

• Changing settings: Be in timekeeping mode and press-and-hold TL for 2 seconds when current city appears in the city box. Pressing TL repeatedly will cycle through the following settings you can modify:

  • Home city
  • Summer time
  • Seconds
  • Hours
  • Minutes
  • Year
  • Month
  • Day
  • 12/24 hour time
  • Date display format
  • Day of week language
  • Toggle tone
  • Illumination duration
  • Auto receive
  • Power saving Use the TR or BR buttons to change the individual settings.

• Solar charging: The display is surrounded by grey solar panels. The current charge is shown by the L/M/H (low/medium/high) bars at the bottom-right. The guide says that half an hour of direct sunlight can keep the watch running for a month.

• Sync manually to atomic time calibration signal: Keep watch in upright position, preferably outside where it is easy to receive a radio signal. Press and hold BR until you see RCVD flashing in top-left corner. It also shows the last date-time when it had synced successfully while it is syncing. In the bottom-right it shows L1/L2/L3 depending how weak/medium/strong the signal is. If sync is successful, after about 10 minutes it shows GET in the top-right corner - press BR to go back to normal timekeeping mode. If sync has failed, it shows ERR in the top-right.

References

• GW-M5610 posts at G-Central