ELECRAFT KRX3 Manuel du propriétaire télécharger pdf (Page 4)

Preventing Electrostatic Discharge Damage

There is no climate or work location where the components of your K3 are safe from Electrostatic Discharge

(ESD) unless you take specific steps to prevent such damage. Many of the components in your K3 can be

damaged by static discharges of only a few volts: far too little for you to notice. It is those low-voltage but

destructive discharges that easily happen anywhere and under virtually any environmental conditions.

ESD damage may not be apparent at first. The damaged components may not fail completely. Instead, the

damage may result in below-normal performance for an extended period of time before you experience a total

failure.

How ESD Damage Occurs

Whenever an object containing a static charge touches a circuit in your K3, current will rush into the circuit until

the components reach the same voltage as the source of the static charge. If the voltage or current that passes

through a component during that brief period exceeds its normal operating specifications, it may be damaged or

destroyed.

Preventing ESD Damage

ESD damage cannot occur if there is no voltage difference between the components in your K3 and any object

that touches them. That is how anti-static packaging works. Anti-static bags allow the static charge to flow over

their surface, so that any part of the bag that touches the components inside are all at the same potential at all

times. Anti-static foam keeps the leads of sensitive components at the same potential.

At your work bench, avoiding a dangerous voltage is achieved most easily by tying everything together and

connecting them to a common mains safety ground. This includes your K3, individual boards or other sensitive

components as well as everything they may touch at the work table.

Inexpensive static dissipating work mats are readily-available that will steadily and safely drain off any charges

built up on parts or circuit boards placed on them. They are supplied with a lead that connects the mat to the

common workbench ground. Also, metal cabinets on test equipment used on the bench should be tied together

and connected to the common ground.

Most importantly, you must have a way of continuously draining off any static charges that occur on your body.

Such charges are easy to create, even while sitting quietly at the work bench. Moving your feet on the floor,

shifting position in your chair or even moving your arms so that clothing rubs against itself can produce

destructive static charges. You can discharge yourself by touching an unpainted metal ground, but that will last

only until you move in a way that produces a new static charge. The safest technique is to wear a grounded wrist

strap with a series 1-megohm resistor that continuously drains off any charges. Such wrist straps are readily-

available and inexpensive.

WARNING

DO NOT attach a ground directly to yourself without a current-limiting resistor as this poses

a serious shock hazard. A wrist strap must include a 1-megohm resistor to limit the current

flow. If you choose to touch an unpainted, metal ground to discharge yourself, do it only

when you are not touching any live circuits with your other hand or any part of your body.

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ELECRAFT KRX3 Manuel du propriétaire Page 4