BSWA 308/309 BSWA Technology Co., Ltd
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4.4.6 RTC Calibration
In the menu of Data & Time,
Press <◄>、<►>、<◄>、<►>、
<Menu/Pause>、<◄>、<◄>、<►>、
<►>、< Menu/Pause > can enter
the RTC Calibration screen.
RTC and MCK are the clocks
used for timing when the sound level meter is turned off and on, respectively. When the
sound level meter is turned on, it will read the date and time in RTC once, and then convert to
MCK timing.
The RTC has been calibrated in the factory, but the MCK clock is not and cannot be
calibrated. Only the default value of "1065" is preset to MCK factor. In general, users can use
this default value to achieve a clock accuracy of about + / - 20 ppm (maximum error of 1.7 s
per day) when the sound level meter is turned on. For better MCK clock accuracy, users can
manually adjust the MCK factor. The calculation formula of MCK factor is as following:
If MCK factor is 1065, the daily error is +0.01 s. If the user wants to speed up the time by 1
s, the calculated MCK factor is 1003, and the error is +1.01 s. If the user wants to slow down
for 1 s, the calculated MCK factor is 1136, and the error is -1.002 s.
Although RTC has been calibrated in the factory, the RTC quartz crystal still has the
characteristics of aging with time. In the long-term running, the clock accuracy will change
slowly. If users find that the RTC clock has become inaccurate, the RTC factor can be
manually adjust. The adjustable range is from -511 to +512, and the corresponding
adjustment is about 0.954ppm (0.08 s per day) for each change in the number of RTC factor.
The RTC factor should be increased to speed up the clock, and vice versa.
★Note: Automatic calibration of RTC is only carried out in the factory, and customer should
not carry out it by themselves.
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