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Agilent E1412A Multimeter Application Information
DC Current Measurement Errors
When you connect the multimeter in series with a test circuit to measure
current, a measurement error is introduced. The error is caused by the
multimeter's series
burden voltage
. A voltage is developed across the wiring
resistance and current shunt resistance of the multimeter as shown below.
True RMS AC Measurements
True
RMS
responding multimeters, like the E1412A, measure the “heating”
potential of an applied signal. Unlike an “average responding”
measurement, a true
RMS
measurement can be used to determine the power
dissipated in a resistance, even by non-sinusoidal signals. The power is
proportional to the square of the measured true
RMS
voltage, independent of
waveshape. An average responding ac multimeter is calibrated to read the
same as a true
RMS
meter for
sinewave inputs only
. For other waveform
shapes, an average responding meter will exhibit substantial errors as shown
below.
The multimeter's ac voltage and ac current functions measure the ac-coupled
true
RMS
value. This is in contrast to the ac+dc true
RMS
value shown above.
Only the “heating value” of the ac components of the input waveform are
measured (dc is rejected). For non-offset sinewaves, triangle waves, and
square waves, the ac and ac+dc values are equal since these waveforms do
not contain a dc offset. Non-symmetrical waveforms, such as pulse trains,
contain dc voltages which are rejected by ac-coupled true
RMS
measurements.
An ac-coupled true
RMS
measurement is desirable in situations where you
are measuring small ac signals in the presence of large dc offsets such as
when measuring ac ripple present on dc power supplies. There are situations,
however, where you might want to know the ac+dc true
RMS
value. You can
Summary of Contents for Agilent E1412A
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Page 10: ...8 Contents Notes...
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Page 26: ...24 Agilent E1412A Multimeter Module Setup Chapter 1 Notes...
Page 194: ...192 Agilent E1412A Multimeter Error Messages Appendix B Notes...
Page 201: ...Index 199 Index Agilent E1412A User s Manual and SCPI Programming Guide...
