Toshiba Portege R930 - Manual (Page 74)

Avoid swiping with your finger stiff or pressed too hard onto the
sensor, and take care to ensure that the center of the fingerprint is
touching the sensor before swiping. Either of these conditions may
cause fingerprint reading to fail.
Check the center of the fingerprint whorl before swiping and then
ensure this is swiped along the center line of the sensor.
There is a possibility of authentication failures if the finger is swiped
too quickly or too slowly - follow any on-screen instructions to adjust
the speed used during the swipe process.
Points to note about the Fingerprint Sensor
Please be aware of the following considerations when using the fingerprint
sensor. A failure to follow these guidelines might result in damage to the
sensor, sensor failure, fingerprint recognition problems or a lower
fingerprint recognition success rate.
Do not scratch or poke the sensor with your nails or any hard or sharp
objects.
Do not press the sensor strongly.
Do not touch the sensor with a wet finger or any wet objects - keep the
sensor surface dry and free from water vapor.
Do not touch the sensor with a soiled or dirty finger as minute foreign
particles of dust and dirt may scratch it.
Do not paste stickers or write on the sensor.
Do not touch the sensor with a finger or any other object which may
have a build-up of static electricity on it.
Observe the following before you place your finger on the sensor whether
for fingerprint enrollment/registration or recognition.
Wash and dry your hands thoroughly.
Remove static electricity from your fingers by touching any metal
surface. Static electricity is a common cause of sensor failures,
especially when the weather is dry.
Clean the sensor with a lint-free cloth - do not use detergent or any
other chemicals to clean the sensor.
Avoid the following finger conditions for enrollment or recognition as
they may result in fingerprint enrollment errors or a drop in the
fingerprint recognition success rate
Soaked or swollen finger, for example as may occur after taking a
bath.
Injured finger
Wet finger
Soiled or oily finger
Extremely dry skin condition on finger
Observe the following to improve the fingerprint recognition success rate.
User's Manual 3-9