Tweco Grounding For Mechanized Systems - Manual (Page 3)

To test for a proper earth ground, refer to the follow-
ing diagram. Ideally, the reading on the multimeter
should be as follows:
• For 115VAC: 3.0 VAC
• For 230VAC: 1.5 VAC
CAUTION
No other connections should be made at the ground
rod being tested.
This test assumes the 115 or 230 VAC source neu-
tral is connected to the utility earth ground.
Art # A-02971
+
_
Meter set to
VAC setting
Ground Rod
Neutral
Line (Hot)
100W
Light Bulb
115 or 230VAC
WARNING
Use extreme caution. This
test uses live voltage.
115VAC: 3.0 VAC
230VAC: 1.5 VAC
V ~
V
~
VR COM A
Ground Testing
2. Increasing the ground rod length beyond 20 - 30 ft
(6.1 – 9.1 m) does not generally increase the effective-
ness of the ground rod. A larger diameter rod which
has more surface area may help. Sometimes keeping
the soil around the ground rod moist by continuously
running a small amount of water into it will work.
Adding salt to the soil by soaking it in salt water may
also reduce its resistance. When these methods are
used, periodic checking of the ground resistance is re-
quired to make sure the ground is still good.
D. Routing Of Torch Leads
1. To minimize RF interference, position torch leads as
far as possible from any CNC components, drive mo-
tors, control cables, or primary power lines. If cables
have to pass over torch leads, do so at an angle. Do
not run the plasma control or other control cables in
parallel with the torch leads in power tracts.
2. Keep torch leads clean. Dirt and metal particles bleed
off energy, which causes difficult starting and in-
creased chance of RF interference.