3M 718A Інструкція з експлуатації - Сторінка 5

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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

) 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