SW-BA-e-2020
31
With the arrow keys <▲>
, <▼>
you can select
the date format and change the date. With the
arrow keys <◄>
, <►> you can
select the year,
month and day, and with the arrow keys <▲> ,
<▼> you can modify their value. Press
<Enter>
to
save
the
setting.
Changing the time setting is similar. Use the arrow keys <◄>
, <►>
to
select hour, minute and second and use the arrow keys <▲> ,
<▼> to modify the value. Press
<Enter> to
save the setting.
The voltage supply for RTC is provided by an internal buffer battery.
Replace the RTC battery if the sound pressure meter forgets the
date and time because the voltage of the RTC battery is too low.
Tips for replacing the RTC battery: Loosen the 5 screws on the back of the sound
pressure meter so that you can remove the cover. The RTC battery is located on the
circuit board as shown in the following figure The battery is a CR-1220 button cell.
☆
Note : The system clock of the sound level meter was calibrated with a reference
clock with an average error of 2 ppm (maximum error 3 ppm). The time accuracy is
less than 10 ppm at room temperature (<26 seconds within 30 days). The maximum
time error for internal tests at 25 °C was about 5 to 8 seconds.
The accuracy of the system clock may vary
depending on the temperature, as there is no
temperature compensation. With the typical
temperature curve in the illustration, the system
clock does not change its base frequency. If the
temperature rises or falls, the frequency of the
system clock changes by about -0.04 ppm/
°
C
²
.
Therefore, if the temperature is 0
°
C, the value for
the system clock changes by -0.04 x (0-25)
²
= -25
ppm, which corresponds to a delay of 2.16 seconds per day. When the temperature is
40
°
C,
the value of the system clock change is -0.04 x (40-25)
²
= -9 ppm, which
corresponds to a delay of 0.78 seconds per day.
The maximum error (<10 ppm) specified in the user manual can
be calculated
as an
approximately 16
°
C
difference from the reference temperature of 25
°
C. The system
clock RTC can therefore
keep
the error
below 26 seconds
within 30 days between 9
°