Idiomas disponibles
Idiomas disponibles
3 Features and Functions
Signal conditioning, ranging, and amplification
Analog input signals are multiplexed into the internal DMM's signal-conditioning section - typically comprising
switching, ranging, and amplification circuitry. If the input signal is a DC voltage, the signal conditioner is composed
of an attenuator for the higher input voltages and a DC amplifier for the lower input voltages. If the input signal is an
AC voltage, a converter is used to convert the AC signal to its equivalent DC value (true RMS value). Resistance
measurements are performed by supplying a known DC current to an unknown resistance and measuring the DC
voltage drop across the resistor. The input signal switching and ranging circuitry, together with the amplifier
circuitry, convert the input to a DC voltage which is within the measuring range of the internal DMM's analog-to-
digital converter (ADC).
You can allow the instrument to automatically select the measurement range using autoranging or you can select a
fixed measurement range using manual ranging. Autoranging is convenient because the instrument automatically
selects the range to use for each measurement based on the input signal. For fastest scanning operation, use
manual ranging for each measurement (some additional time is required for antoranging since the instrument has to
make a range selection.
Analog-to-digital conversion (ADC)
The ADC takes a prescaled DC voltage from the signal-conditioning circuitry and converts it to digital data for output
and display on the front panel. The ADC governs some of the most basic measurement characteristics.
These include measurement resolution, reading speed, and the ability to reject spurious noise. There are several
analog-to-digital conversion techniques but they can be divided into two types: integrating and non-integrating. The
integrating techniques measure the average input value over a defined time interval, thus rejecting many noise
sources. The non-integrating techniques sample the instantaneous value of the input, plus noise, during a very short
interval. The internal DMM uses an integrating ADC technique.
Main processor
The main processor, located in the floating logic section, controls the input signal conditioning, ranging, and the
ADC. The main processor accepts commands from, and sends measurement results to, the earth referenced logic
section. The main processor synchronizes measurements during scanning and control operations. The main
processor uses a multi-tasking operation system to manage the various system resources and demands.
The main processor also calibrates measurement results, performs Mx+B scaling, monitors alarm conditions,
converts transducer measurements to engineering units, time stamps scanned measurements, and stores data in
non-volatile memory.
Keysight DAQ970A/DAQ973A User's Guide
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