Page 314 - Electromechanical Devices and Components Illustrated Sourcebook

276 Electromechanical Devices & Components Illustrated Sourcebook

Alligator Clip

Test Lead Wire
Tip Safety
Ground
Resistor Housing

25 KV Max.

Handle
Output
Coaxial Cable
Dual Banana Plug
Figure 16-5 High-Voltage Probe

he simply returned it to the instrument room. To make matters Isolating high voltages is principally a function of dis-
worse, the technician who was killed was working alone. Had tance. Any material or media has a distance or thickness per
he followed proper safety procedures, he would have had a volt that it will stand off. As an example, the general rule of
safety technician present who could have applied cardiopul- thumb is that air will stand off 20,000 volts per inch. Many
monary resuscitation (CPR) and, most likely, saved his life. factors, such as humidity, airborne dust, magnetic fields, and
Figure 16-5 shows a typical high-voltage probe. These the like, can affect this figure.
devices should be cleaned, inspected, and qualified on a reg- Controls are typically isolated by using plastic drive or
ularly scheduled basis. If the probe receives any damage push shafts, as shown in Figure 16-6. The shaft should be suf-
whatsoever, it should be immediately taken out of service. ficiently long to prevent any chance of arcing along its length.
Never use a high-voltage probe without connecting its safety The control panel should be constructed from a grounded
ground clip to a known ground. piece of sheet metal with metal shaft collars. In this manner,

Grounded Metal Panel
Shaft Coupler Metal Stub Shaft
Return Spring
Insulating Push Shaft Button
Spring Keeper

Push Button

Alignment Cup
Component Floating Metal Shaft Collar
at High Voltage

Grounded Metal Panel
Shaft Coupler Shaft Coupler Metal Stub Shaft
Control Knob
Insulating Drive Shaft

Rotation

Component Floating Metal Shaft Collar
at High Voltage

Figure 16-6 High-Voltage Isolation Methods