Agilent Technologies N1022A Manuel d'utilisateur télécharger pdf (Page 26)

Current Probes Overview

Current probes sense the current

flowing through a conductor and

convert it to a voltage that can be

viewed and measured on an oscil-

loscope. There are two types of

current probes for oscilloscopes,

ac current probes (usually pas-

sive probes) and ac/dc current

probes (usually active probes).

Both types use the same principle

of transformer action for sensing

ac current in a conductor. The

alternating current flowing

through a conductor causes a flux

field to build and collapse accord-

ing to the amplitude and direc-

tion of current flow. The ac cur-

rent probe head is actually a coil—

when placed in this field the

changing flux field induces a volt-

age across the coil. The ac/dc cur-

rent probes also contain a Hall

Effect device to sense dc and low

frequency ac. Because dc doesn’t

cause a changing flux field it can-

not be sensed by transformer

action. Also, at frequencies very

close to dc, the flux field may not

change fast enough for measura-

ble transformer action.

Figure 5.2. Agilent 1147A general-

purpose ac/dc current probe.

Model Probe Type Applications and Use Page

1146A ac/dc Current Measure dc and ac current simultaneously. Useful for 27

lines type power measurements.

1147A ac/dc Current Measure dc and ac current simultaneously. Useful for 29

pwm/switching power measurements.

Current Probe Advantages Limitations

1146A low-cost model measures ac and dc current 100 kHz bandwidth

to 100 Arms without breaking into the circuit

1147A measures ac and dc current to 50 MHz 15 A rated current

without breaking into the circuit

Figure 5.1. Agilent 1146A low-cost

ac/dc current probe.

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Agilent Technologies N1022A Manuel d'utilisateur Page 26

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