Agilent Technologies U1270 Series Spezifikationen PDF herunterladen (Seite 6)

Multimeter Basic Features

Temperature measurement

The maximum temperature range measurement capability of a DMM is limited

by the type of thermocouples that can be used with the unit. Check which types

of thermocouples are supported by the DMM to ensure compatibility with your

application needs. For example, for maintenance of an air conditioner’s com-

pressor, it is sometimes necessary to obtain the temperature difference at the

inlet and the outlet of the compressor. With a dual and differential temperature

function, the two temperature measurements can be made simultaneously, the

differential temperature computed automatically, and the results displayed on

the DMM screen.

Capacitance measurement

DMMs also provide the ability to measure capacitance. Before purchasing a

DMM, make sure that it covers the anticipated capacitance range. Most DMMs

can measure from a few picofarads to at least 1 microfarad. It should be noted

that a capacitor measurement obtained with a handheld DMM can be substan-

tially different from the same capacitor measurement result obtained using an

LCR meter. This is because the LCR meter is testing the capacitor with an AC

signal that has a known frequency. This measurement technique provides highly

accurate readings, as well as additional data such as dissipation factor, mag-

nitude, and phase. The handheld multimeter uses a precise current source to

charge through the capacitor which is characterized by the equation I = C dV/dt.

By observing the rate of change on the voltage across the capacitor, the capaci-

tance can be computed. However, undesirable capacitor traits such as dielectric

absorption, leakage, dissipation factor, and equivalent series resistance (ESR)

can cause substantial error when using this type of measurement technique. If

you require precise capacitance measurements, an LCR meter should be used

rather than a handheld multimeter.

Frequency measurement

Maintaining the right frequency is crucial for electrical devices that rely on a

steady AC voltage and current. The frequency measurement function is ideal

for simultaneous monitoring of real-time voltage or current with frequency, duty

cycle, or pulse width. However, it’s important to realize that not all DMMs sup-

port frequency measurement.

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Agilent Technologies U1270 Series Spezifikationen Seite 6