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Why am I experiencing a temperature increase in my
Defender 520?
A temperature rise during initial battery charging, or while
charging a fully discharged battery is normal. To maintain the
best possible accuracy Bios recommends fully charging your
battery before taking measurements. If this is not possible, we
recommend disconnecting your Defender from its AC power
adapter/charger while taking flow measurements – or to run
gas through your Defender for 10 minutes before starting the
flow measurement.
Why doesn’t my piston return to the bottom of the cell?
If the piston fails to return to the bottom of the cell after a
measurement this could be caused by:
• A discharged battery not providing enough power to operate
the internal valve properly (Try charging the Defender)
• Bright light shining into the unit resulting in an overload
of the internal optical sensors (Try to operate the unit in
a shaded location)
• Moisture or dirt inside the cell (Return the Defender to
Bios for service)
10.0
What is Dead Volume ?
Dead Volume is the gas volume between a flow generator
and the instrument taking the measurement. Since gas is
compressible, this gas can act as a spring between the flow
source and the measurement instrument. For best accuracy
this volume should be kept to a minimum.
We recommend keeping the tubing length between the
gas flow generator and your Defender to no more then
.5 meters/20 inches in length.