External Power Supply - Arexx BS-750SD Mode D'emploi

USB
USB-implementations may vary from PC to PC, which mostly seems to cause
some problems at connecting and disconnecting (respectively switching on
and switching off) the computer. Sometimes even the disconnected PC will still
provide the USB-connector with the standard amount of specified DC-power.
Under such conditions the BS-750SD will operate without the need for an
external power supply. In other cases, in which the USB-connector does not
provide DC-power, an external power supply will be needed to allow the BS-
750SD to collect measurement data during the offline-periods of the PC.

External power supply

The module will operate in stand-alone mode as long as an external power
supply delivers the required DC-power. Data will be stored in the internal
data-flash memory and on the SD-card (if an SD-card has been installed). As
soon as the DC-power is being removed and the module switches off, a tiny
set of the most recent data records may be missing in the internal data-flash
memory. This effect is caused by a data-cache (intermediate storage) method,
in which data is being collected before writing a complete record set to the
flash memory. These losses will not occur in data sets, which have been recor-
ded on the SD-card, in which each measurement data set is being recorded
individually.
Internal real-time clock
The BS-750SD module uses an internal clock (RTC) to supply measurement
data with a time-stamp. With the help of a small battery (a button cell type:
CR2032) this clock will also be operating uninterruptedly in a switched-off
module.
The clock will be synchronized by the Multilogger software as soon as a data
link has been established. If the clock restarts – for instance to be caused by
an empty button cell – the missing time-stamp prevents the system to record
new data. The error will cause both indicator LEDs to flash simultaneously.
The error status may be removed by connecting the module to the PC in order
to synchronize the module with the Multilogger software. The software will
synchronize the clocks, which allows the Multilogger process to restart further
logging.
It is easy to replace the button cell battery. The button cell can be found at the
printed circuit board, which is made accessible by opening both halves of the
BS-750SD compartment.
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