Tingling Sensation Explanation
A tingling sensation may be noticed when connecting devices to Dell laptop computers or printers and touching exposed metal parts of the devices being connected or the parent device. This tingling sensation can occur any time the AC adapter is connected and the user touches any exposed metal surface on the computer, the printer, the PDA, etc. This may lead to the conclusion that the device is unsafe. The electric current on all Dell products have been measured and proven to be well within the safety limits per safety standards - IEC950, EN60950, UL1950, etc., even with an input voltage of 240 Volts. The voltage (tingling sensation) does NOT present any risk of injury to the user. It is recommended to unplug the AC adapter from the parent device before attaching any cables or accessories, as this reduces the possibility of experiencing the tingling sensation.
Technical Reasons for Experiencing a Tingling Sensation
All electrical devices, including laptops, printers, PDAs, etc., powered by AC Adapters with a two-pronged power cord (without a ground wire) may exhibit an electrical potential (voltage) between the exposed metal parts of the device and earth ground. The human body can be thought of as a wire which can conduct electric current. Depending on the conditions of a person's skin -- oily, dry, etc., and the surrounding environment (humidity level, flooring or desk material) -- the body can be more or less conductive. If conditions are right for the human body to be less conductive, such as having dry hands or wearing rubber soled shoes on a carpeted floor, the probability of sensing the tingling (electric current) is reduced. If conditions are right for the human body to be more conductive, such as having wet hands or standing barefoot on a concrete floor, the probability of sensing the tingling (electric current) increases.
Connecting multiple devices that use two-pronged power plugs increases electrical potential between exposed metal parts, thus increasing the potential of feeling a tingling sensation.
The voltage potential between exposed metal parts of the device and earth ground can be observed using various voltage measuring devices:
- It is possible to measure a voltage potential between 0 and 100 Volts or possibly higher.
- If a high impedance-measuring device (i.e., oscilloscope or digital voltmeter) is used, the voltage can be measured as high as 70 Volts or higher.
- If a low impedance-measuring device (analog voltmeter) is used, the measured voltage should be 30 Volts or lower.
The lowering of the voltage can be demonstrated by using a high impedance-measuring device and then touching the metal back plate of the computer; the voltage will drop, due to the lower impedance of the human body.