Hardy HI 200DNWM DeviceNet Weigh Module - Manual (Page 59)

CHAPTER 8 - TROUBLESHOOTING
8-5
Electrical See Figure 8-4
FIG. 8-4 GUIDELINES FOR INSTABILITIES ON FORMERLY OPERAT-
ING SYSTEMS - ELECTRICAL
Electrical B1
Physical Grounding -
All common equipment share a common ground point.
Keep the ground cable length to earth ground as short as possible.
Install a new ground rod if the cable length is excessive.
Cable -
Cuts or breaks in the loadcell cable insulation allow moisture to wick into the cable
and loadpoints. This can setup stray capacitance charges and allow ground currents
to exist. This could create a highly intermittent situation.
Loadcells -
Ground straps must be installed to provide a direct discharge path to ground around
the loadpoints.
Vessel, Fill and discharge piping -
Ground all to a common point to eliminate electrical differences in potential, and
static build-up.
Cable Routing -
Seperate high voltage sources and cables from low voltage signal cables.
Stay a minimum of 14 inches from Magnetic fields and SCR controls.
Avoid parallel high voltage and signal cable runs.
Cable Shielding -
Ground low voltage cable shields only at the controller end.
Grounding both cable ends will produce ground currents.
Verify, with an ohm meter, the shield is only grounded at the weight controller.
Disconnect the shield at the controller and check for an open circuit between ground
and shield. Reconnect the shield to ground and confirm a proper ground path from
the Junction box to the controller.
Verify the shield is not connect to ground at the Junction Box.
Loadcell cable shields only pass thru the Junction Boxes and are not connected to
ground at that point.
B1.1
B1.3
B1.2
B1.4
B1.5
B1.6
GOTO
B