Flowline LI90 Commander - Manual (Page 12)

12 of 57 PRELIMINARY MANUAL 27 AUG 08
Commander LI90 Series Rev 1_3
Electrical
• Grounding Definition
o Ground: The term Ground is defined as a conductive connection between a
circuit or piece of equipment and the earth. Grounds are fundamentally used to
protect an application from harmful interference causing either physical damage
such as by lightning or voltage transients or from circuit disruption often caused
by radio frequency interference (RFI).
• Ground Specifications
o
Ideally, a ground resistance measurement from equipment to earth ground is 0 ohms.
In reality it typically is higher. The U.S. National Electrical Code (NEC) states the
resistance to ground shall not exceed 25 ohms. Flowline recommends less than 15
ohms resistance from our equipment to ground. Resistance greater than 25 ohms can
cause undesirable or harmful interference to the device.
• How to Test for Good Ground
o
In order to test ground resistance, a Ground Resistance Tester must be used. A
typical Ground Resistance Meter Kit contains a meter, two or three wire leads,
and two ground rods. Instructions are supplied for either a two-point or three-
point ground test. Below shows a two-point ground connection test.