A HOLD notice will also be
displayed to alert the user that the
instrument is currently in HOLD
status. To unfreeze the display and
return to floating measurement,
momentarily press the HOLD switch
once again. Please note that during
HOLD condition the distance-
indicating LED’s are turned off.
3.5 Zero adjustment: the 3M™ 718 Static
Sensor has a zero adjustment
function, which sets a zero reference
point for all subsequent
measurements. This zero reference
can be set by pointing the instrument
at a known zero-voltage surface, and
holding down the RANGE/ZERO
button for longer than 3 seconds.
After 3 seconds, the display will flash
and adjust to zero. Repeat this step
for both the 2 kV and the 20 kV
ranges. The zero adjustment should
be performed every time the unit is
turned on.
3.6 Measurement Accuracy:
3.6.1 Distance Indicator: the 718 Static
Sensor is factory calibrated to give
accurate measurements when it is
placed one inch (2.54 cm) away
from the object to be measured. To
assist the user in gauging this
distance, two light-emitting diodes
(LED’s) are present on the front face
of the instrument. These LED’s
emit two red, bullseye targets on the
surface of the object being measured.
As the instrument gets closer to the
one inch measurement distance, the
bullseyes begin to converge. When
they converge and become one, the
instrument is approximately one
inch away, and the measurement can
be made.
For more accurate measurements,
it is recommended that the user
manually measure the distance
between the front housing of the
instrument and the object
being measured.
3.6.2 Accuracy and Size of Object to be
Measured: the minimum surface
area on an electrostatically charged
object which can be accurately
measured is a 5 square inch
(32.3 cm
2
) area.
3.6.3 Measurements from Greater than
One Inch (2.54 cm) Away: in the
event that a one inch separation
between object-to-be measured and
the 718 cannot be achieved, it is
possible to get approximate
readings. This can be accomplished
by holding the instrument at
multiples of one inch (two inches,
three inches, etc.) away from the
object. The measurement reading is
then adjusted according to the
following equation:
Measurement distance (in inches) x
displayed voltage (in kilovolts) =
approximate voltage in kilovolts
