Appendix B: Grounds And Floating Operations; Ground Definitions; Grounding In The Reference 30K Booster; Grounding In The Reference 3000 Potentiostat - Gamry Instruments Reference 30k Booster Operator's Manual

Table of Contents

Appendix B: Grounds and Floating Operations

Ground is an electronics term that is often misunderstood. In non-technical English, one meaning of the word

ground is the surface of the planet Earth on which we all live. In technical English, the definition of ground

usually involves a point with an electrical connection to Earth. In this section, we will call this type of ground

earth ground, or earth.

Knowledgeable electronics engineers use a somewhat different definition for the term ground. Ground is a

common point in a circuit. Some English-speaking countries use the term earth instead of ground. Voltages are

referred to this ground point as though it were at zero volts. A ground that functions as a reference point in a

circuit, but is not connected to Earth, can be called a floating ground.

The metal case of the Reference 30k Booster is connected to earth ground via the ground pin in the AC power

(mains) cord. This connection is essential to the electrical safety of this instrument. As defined in IEC Publication

348, Safety Requirements for Electronic Measuring Apparatus, the Reference 30k Booster is a Class I apparatus.

Class I apparatus is only safe from electrical-shock hazards if the case of the apparatus is connected to a

protective earth ground. In the Reference 30k Booster, the Protective Ground is available on a binding post on

the rear of the Reference 30k Booster. This binding post is green and identified with the standard symbol for

protective earth ground:

The green binding post is only provided as a convenient access point for the protective earth

ground. This binding post is connected to the instrument chassis, which, in turn, is connected to the third

wire in the power cord for the Booster. The instrument is electrically safe with no connection to this point.

The internal circuitry of the Reference 30k Booster is not referenced to this Protective Ground. Instead,

voltages within the Reference 30k Booster's chassis are measured with respect to a Floating ground, labeled

System Ground.System Ground is used as the zero-volt reference point for the Reference 30k's power supplies

and other circuitry. A black binding post on the Reference 30k Booster's rear panel allows easy access to this

(floating) System Ground.

Unlike the Reference 30k Booster, the circuitry and the metal case of the Reference 3000 potentiostat are not

connected to earth ground. The Reference 3000 is an IEC Publication 1010 Class II apparatus, in which contact

with all hazardous voltages are prevented by means of "reinforced insulation".

Like operation of the Reference 30k Booster, voltages within the Reference 3000 chassis are measured with

respect to a floating ground, which is the zero-volt reference point for its power supplies and other circuitry.

Unlike the Booster, the Reference 3000 chassis is connected to the floating ground.

Grounds and Floating Operations

Table of Contents