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4 Safety
4.3 Electrostatic charge
ESD
ESD protective measures
Training
What is an electrostatic charge?
Formation of an electrostatic charge
Amount of charge
14
4.3.2
ESD protective measures
ESD stands for ElectroStatic Discharge.
ESD protective measures include:
● Procedures for preventing electrostatic charge build-up (e.g. air
conditioning, air moistening, conductive floor coverings and non-
synthetic clothing)
● Discharging the electrostatic charges of your own body on the frame
of the UNIT, the protective ground wire or large metallic objects
● Connecting yourself to ground using a wrist band.
We therefore recommend that all persons working with this system be
instructed on the significance of this warning label. Furthermore, they
also should receive training in the physics of electrostatic discharges
which can occur in the practice and the destruction of electronic
components which may result if such components are touched by
electrostatically charged USERS.
The content of this training is explained in the Chapter "About the
physics of electrostatic charges" [→ 14].
4.3.3
About the physics of electrostatic charges
An electrostatic charge is a voltage field on and in an object (e.g. a
human body) which is protected against conductance to ground
potential by a nonconductive layer (e.g. a shoe sole).
Electrostatic charges generally build up whenever two bodies are
rubbed against each other, e.g. when walking (shoe soles against the
floor) or driving a vehicle (tires against the street pavement).
The amount of charge depends on several factors:
Thus the charge is higher in an environment with low air humidity than
in one with high air humidity; it is also higher with synthetic materials
than with natural materials (clothing, floor coverings).
Electrostatic discharge must be preceded by electrostatic charging.
The following rule of thumb can be applied to assess the transient
voltages resulting from an electrostatic discharge.
An electrostatic discharge is:
● perceptible at 3,000 V or higher
● audible at 5,000 V or higher (cracking, crackling)
● visible at 10,000 V or higher (arc-over)
The transient currents resulting from these discharges have a
magnitude of 10 amperes. They are not hazardous for humans because
they last for only several nanoseconds.
Dentsply Sirona
Operating Instructions CEREC Primemill
67 19 681 D3439
D3439.201.01.01.02 09.2019
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