Agilent Technologies U1270 Series Especificações descarregar pdf (Página 9)

Think Safety When Selecting a Handheld DMM

Safety is frequently not given much consideration when selecting a multimeter.

However, different handheld DMMs are designed with different levels of

protection against common electrical hazards. For that reason, one of the most

important considerations in selecting a handheld DMM centers on thoroughly

understanding the test environment and test requirements. Using this knowl-

edge you can choose the appropriate device.

There are three key DMM characteristics to consider:

1. Voltage rating of the circuit

2. Transient voltage rating of the circuit

3. Energy capacity

Voltage rating of the circuit

There are many different mains voltage ratings for the operation of household

and light commercial electrical appliances and lighting. It is important to identify

the maximum voltage at which the circuit is designed to work and, at minimum,

choose a handheld DMM rated to measure the voltage that is expected to be

present on the circuit.

Transient voltage rating of the

circuit

Transient voltages come from two main sources: they can result from natural

causes, such as lightning outside the building, or they can be generated by

switching operations on the power distribution system. Switching events in

power distribution include switching of transformer taps, motors, inductances,

sudden variation of load, or disconnection of circuit breakers. The amplitudes

of these transient voltages vary from a few hundred volts peak to about 6,000 V

peak. These randomly occurring high voltage spikes tend to last from 50 to 200

microseconds.

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Agilent Technologies U1270 Series Especificações Página 9