Miyota caliber 6S30 is a quartz chronograph watch movement. It is made in Japan and has 0 jewels. Miyota is owned by Citizen Watch Co. Ltd.
In Miyota’s own words:
Quick Reset (by Heart Cam Reset System)
Click Feeling Push Button Handling
4 Beats Center Chrono Second Hand
Balanceable Weight of Hands
6S30 VS 6S20:
The Miyota 6S30 is identical to the caliber 6S20, with the major difference being that the two upper subdials (60 minute chronograph counter and 1/20 second) sit higher on the dial to create a more balanced look. On the Miyota 6S20, the handstacks of the upper two subdials sits parallel with the main handstack and crown, placing the 1/20 sec counter at 3:00 and the 60 minute counter at 9:00. With the 6S30, the 1/20 sec counter is at 2:00 and the 60 minute counter is at 10:00. This may allow allow for the appear of larger subdial rings on watches with the 6S30.
Miyota claims that the accuracy of the 6S30 is within +/-20 seconds per month in normal operating temperatures.
According to Miyota, the correct SR927W (395/399) battery cell should last about 4 years in the caliber 6S30. Miyota’s battery life claims are based on using the chronograph function for 60 minutes or less per day. Running the chronograph means the watch is working harder and this reduces the battery life. For that reason, it is advised to only use the chronograph when you need it. If you are not going to wear your watch for a while and want to save the battery, pulling out the stem (aka hacking the movement) will reduce the battery consumption.
Replacing the Battery:
The battery is held in place with tension. Te remove the battery, gently move the tension arm back with your tool to allow the battery to pop out. The install a new battery, make sure the cell slides under the fix tab and hold the tension arm back, push the battery down and slowly release the tension arm back into place with the top tab holding it in place. The “tension arm” as described here is circled in the image below.
Resetting the chronograph to zero:
If your chronograph hand is not resetting to 12:00 or “zero” position, then you can try the following steps:
Pull the crown to position 2 (time setting position).
Press button A to advance the chronograph hand forward until it is lined up with 12:00. If you long-press A, the hand will move forward faster.
Press button B to advance the 1/20 second subdial.
Note: if you push the crown back in to position 0 while the chronograph hand is still advancing forward, then it will stop the chronograph hand and recognize it as zero position. In this case, you will have to start over again.