Monroe Electronics Electrostatic Fieldmeter - Static Monitor - model 177A - Manual (Page 64)

APNE-0016 63
VII. I. Introduction
Content
This document provides the reader with a review of how fieldmeters operate to measure
electric fields, the effects of web-converting machine geometry and operator techniques
when measuring electric fields, how handheld fieldmeters are used to investigate where
static problem areas exist on machines, and techniques for interpreting fieldmeter readings.
This document is the second in a series of three application notes about static charging of
materials and equipment in web converting machines, including recommendations for static
measurement, control, and continuous monitoring. The first document in this series is
application note APNE-0014 Electrostatic Charging In Web Converting.
Review
Generation and control of static in web converting depends upon many varying conditions
in the web material, the converting machine, the surrounding atmosphere, and the static
control measures used on the machine. It is impossible to predict and control all of these
conditions because they can change without one realizing it until a statically caused event
occurs. Changing conditions can alter the amount of static charge accumulation, so
although static is under control today, it may not be under control tomorrow.
The keys to continuous static control are
1. The correct determination of critical areas of the machine to monitor for static
charge accumulation,
2. Application of static countermeasures and devices that prevent or control static
charge accumulation, and
3. Continuous electric field measurement in these critical areas using permanent
fieldmeters, which are alarmed to warn or shutdown the operation when web
static charge levels increase beyond predetermined set points.
VIII. II. Electric Fields and Fieldmeters
Electric Field
An electric field is a region of space characterized by the existence of an electric force (F)
generated by an electric charge (q). The electric force F acting on a charge q in an electric
field is proportional to the charge itself. The relationship of these quantities is expressed by
the electrostatic force law [1]:
F = qE
E is called the electric field strength and is determined by the magnitude and locations of
the other charges acting upon charge q:
E = F/q
The electric field strength, E, is usually displayed in the unit of volt/meter (V/m),
volt/centimeter (V/cm) or volt/inch (V/in).