Figure 7-16.Typical tool tester.
The transformer passes approximately 30 amperes
through the tool cord equipment ground, burning away
any whiskers that may be causing a poor equipment
ground If there is no equipment ground, the OPEN
EQUIPMENT GROUND sensing relay is activated,
and appropriate warnings are given (the OPEN
EQUIPMENT GROUND light glows).
If the resistance of the ground on the equipment
under test is approximately 0.2 to 1.5 ohms, the
FAULTY EQUIPMENT GROUND sensing relay is
activated Resistance in excess of this amount activates
the OPEN EQUIPMENT GROUND sensing relay.
The range in length of extension cords that can be
tested is from approximately 6 feet to 100 feet of 16-
gauge wire. These lengths will be longer or shorter in
other gauges. The sensing circuit can be adjusted for
The presence of a dangerous POWER GROUND,
caused by carbon, moisture paths, or insulation
breakdown, is checked at a 500-volt potential or at a
120-volt potential when the RF TEST button is pressed.
The equipment, line cord, and switch are tested for
Faulty conditions are indicated by the
corresponding light (red) and buzzer. One faulty
condition must be corrected before another one will be
Tests proceed only when the equipment ground is in
a safe condition. All tests (except the power ground) are
conducted at potentials less than 10 volts.
If no electrical defects are found, the tool operates at
its proper voltage to reveal any mechanical faults.
Optional features are installed to simplify two-wire
and double-insulated tool tests and provide for safely
testing double-insulated tools for power grounds.
The tool operates at the end of the test cycle. Be
sure moving parts are faced away from the
operator and have proper clearance to operate.
Remove any removable cutting blade or bit
before the tool is tested Do not come in
physical contact with the tool during the test.