BK Precision 4011A Instrucciones de operaciones descargar pdf (Pagina 44)

Appendix A: Safety

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dential, commercial, and industrial systems, such as lighting and heating, are always grounded

for greater safety. Communication and computer systems, as well as general electronic equip-

ment (e.g., DC power supplies, oscilloscopes, oscillators, and digital multimeters) are grounded

for safety and to prevent or reduce electrical noise, crosstalk, and static.

Ungrounded circuits are used in systems where isolation from other systems is necessary, where

low voltages and low power are used, and where obtaining a suitable ground connection is diffi-

cult or impractical. In an ungrounded circuit, contact with two points in the circuit that are at dif-

ferent potentials is required to produce a shock. The hazard is that, with no specific ground in

such circuits, a hidden fault can cause some random point to be grounded, in which case, touch-

ing a supposedly safe conductor while standing on the ground could result in an electric shock.

Protecting People and Equipment in the Laboratory

Strict adherence to several common-sense rules, summarized below, can prevent electric shock

to individuals and damage to laboratory equipment.

Protecting People

a) When building a circuit, connect the power source last, while the power is OFF.

b) Before changing a circuit, turn off or disconnect the power if possible.

c) Never work alone where the potential of electric shock exists.

d) When changing an energized connection, use only one hand. A common practice is to put

one hand behind your back when touching a circuit that is possibly energized. Never

touch two points in a circuit that are at different potentials.

e) Know and check that the circuit and connections are correct before applying power.

f) Avoid touching capacitors that may have a residual charge. Stored energy in a capacitor

can cause severe shock even after a long period of time.

g) Insulate yourself from ground by standing on insulating mats where appropriate.

The above rules and the additional rules given below also serve to protect instruments and other

circuits from damage.

Protecting Equipment

a) Set the scales of measurement instrument to the highest range before applying power.

b) When using an oscilloscope, do not leave a bright spot or trace on the screen for long pe-

riods of time. Doing so can burn the image into the screen.

c) Be sure instrument grounds are connected properly. Avoid ground loops and accidental

grounding of “hot” leads.

d) Check polarity markings and connections of instruments carefully before connecting

power.

e) Never connect an ammeter across a voltage source, but only in series with a load.

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BK Precision 4011A Instrucciones de operaciones Pagina 44