Safety Precautions For The Electrical System; Electrostatic Discharge (Esd) - Valtra T144 H Service Manual

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Repair
T4 HiTech 8
21.5.2015

Safety precautions for the electrical system

Follow the safety precautions for the electrical system.
IMPORTANT: Make sure that the main power is turned off before disconnecting or reconnecting the battery.
IMPORTANT: Disconnect the negative lead of the battery first and connect it last.
IMPORTANT: Always connect the battery with the correct polarity.
IMPORTANT: Disconnect the negative battery lead before removing the alternator.
IMPORTANT: Never open the charging circuit while the engine is running.
IMPORTANT: Ensure good ventilation when charging.
IMPORTANT: Do not connect any additional electrical equipment, as this may damage components of the existing
electrical system.
IMPORTANT: All electronic equipment is sensitive to electrostatic discharge (ESD). Take all necessary measures
to minimize or eliminate the risk of equipment being damaged by ESD.
IMPORTANT:
The tractor has a negative-earthed alternator that can be damaged easily if incorrect connections are made in the
electrical system. For example, connecting the battery with the wrong polarity can burn the alternator or rectifier.

Electrostatic discharge (ESD)

Electrostatic discharge (ESD) is the sudden and momentary electric current that flows between two objects at
different electrical potentials. Static charges are generated in objects by friction. Uncontrolled, ESD may damage
the sensitive instruments of components such as circuit boards. With help of earthing, the static charge can be
discharged in a controlled way.
Immediate ESD induced defects lead to an obvious deterioration or complete failure of the component. However,
detecting slighter ESD damage can be difficult as electrostatic discharge does not necessarily destroy the entire
device. Its functionality may be disrupted partially, or the device may even seem to function properly, but its lifetime
reduces dramatically. Sometimes, such damages are not detectable in testing. Hidden defects are usually detected
only after the component or device breaks down completely. In complex devices and systems, finding and
replacing a single defective component is difficult and expensive.
ESD events may occur without visible or audible sparks. Circuit boards can be damaged by static electricity
discharges as low as 100V, which is a fraction of the voltage levels that can be detected by human senses.
When ESD sensitive elements such as circuit boards are handled, the requirements of the component
manufacturer and the ESD standard IEC 61340-5-1 and technical report IEC/TR 61340-5-2 must be complied with.