64 Chapter 3 Configuring for Measurements
Analog RMS Conversion The analog RMS conversion directly integrates the input signal and is the
method selected when power is applied. This method works well for
measuring signals in the frequency range of 10 Hz to 2 MHz and can provide
the fastest reading rate of the three methods.
Random Sampling
Conversion
The random sampling conversion takes numerous samples of the input signal
for each reading generated. Samples are spaced randomly by an internal time
base generator and the signal's true RMS value is calculated statistically.
Random sampling does not require a repetitive input signal (as does
synchronous sampling) making it suitable for applications such as wideband
noise measurements. This method has excellent linearity, good accuracy, and
is particularly suited to low-level (<l/10 of full scale) measurements. The
measurement bandwidth for random sampling is 20 Hz to 10 MHz.
Specifying the AC
Voltage Method
When power is applied, the multimeter selects the analog RMS conversion.
In the power-on state, you can make measurements using the analog RMS
conversion simply by selecting AC or AC+DC voltage measurements as
follows:
OUTPUT 722;"ACV"
!SELECTS AC-COUPLED AC
VOLTAGE MEASUREMENTS
or
OUTPUT 722; "ACDCV"
!SELECTS DC-COUPLED AC
VOLTAGE MEASUREMENTS
The SETACV command allows you to specify the AC voltage measurement
method. For example, to specify the random sampling conversion, send:
OUTPUT 722;"SETACV RNDM"
To select the synchronous sampling conversion, send:
OUTPUT 722;"SETACV SYNC"
To return to the analog RMS conversion, send:
OUTPUT 722;"SETACV ANA"
The specified AC voltage measurement method remains in effect until power
is cycled, the multimeter is reset, or another method is specified. Whenever
you select AC or AC+DC voltage measurements, the last specified (or
power-on) measurement method will be used.
AC or AC+DC Current The multimeter measures current by placing an internal shunt resistor across
the input terminals, measuring the voltage across the resistor, and calculating
the current (current =voltage/resistance). Unlike AC or AC+DC voltage
measurements, AC or AC+DC current measurements can be made using the
analog method (direct integration) only. The multimeter's front and rear
current inputs are protected by 1 A, 250V fuses. Figure 12 shows the front
terminal connections for all types of current measurements.
The multimeter measures AC or AC+DC current on any of five ranges. For
AC current measurements, the multimeter measures only the AC component
of the input signal, For AC+DC current measurements, the multimeter
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