User Manual

ACL 450B Operation Manual Rev. Jan 10, 2022 MKB

Page 4 of 6

3. Set distance

For voltages between 19.99kV to +19.99kV, move the sensor plate of the instrument toward the

target surface. When the instrument is the correct distance (1 inch) from the target, the projected

range finder appears as a stationary concentric ring. To read voltages of 20 kV, use the distances and

multiplying factors given under Range in Specifications.

4. MEASURE and HOLD

Once the meter is zeroed, point the sensor 1 inch from the object being measured. Depress the

MEASURE/HOLD pushbutton so it releases to the upper HOLD position. This will freeze the reading

and allows the operator to move the meter where it may be more easily read or saved for later

reference.

In the HOLD position, the red LED will light. The analog output signal is also held. The concentric rings

will no longer be projected. When the pushbutton is returned to the MEASURE position, concentric

rings will be projected.

5. Turn the instrument OFF

Slide power button to the OFF position.

7. Display

If the numeral 1 appears on the left side of the 450B display, the meter’s range of 20 kV per inch has

been exceeded. When this occurs, move the meter farther away from the object and multiply the

reading by the distance away from the object being measured. For example, if the meter is 2 inches

(51mm) from a surface with a 30kV charge, the display will indicate 15kV.

The measurement accuracy is dependent on a stable ground reference and the measuring distance

plus the aspect ratio that relates the size of the object to be measured to the measurement distance.

This aspect ratio should be at least 4:1 for best accuracy, i.e., the surface should be at least a 4-inch

(102mm) square when measuring at a 1-inch (25mm) distance.

CAUTION:

If you bring the instrument (or any grounded object) too close to a charged surface, an electrical arc

may occur. To avoid this and take readings safely, check the voltage/distance ranges given in

Specifications. Always bring the instrument toward a target surface from a distance of several inches.

As the distance closes, watch the display to be sure that the proper distance is maintained for each

voltage range.