Dds Assembly (A6) - Fluke 5520A Service Manual

NORMAL
HI
C =
x
NORMAL
LO

2-4. DDS Assembly (A6)

The DDS (Direct Digital Synthesis) assembly (A6) contains the following blocks:
References for all voltage and current functions.
Gain determining elements for voltage functions and thermocouple measuring and
sourcing.
7 V references.
Thermocouple sourcing and measuring amplifier.
An A/D (Analog-to-Digital) measurement system for monitoring all functions.
Self-calibration circuitry.
Zero calibration circuitry.
Precision voltage channel DAC (VDAC).
Precision current channel DAC (IDAC).
Dual-channel DDS (Direct Digital Synthesizer).
These functional blocks, when used with the Voltage (A8) and/or Current (A7)
assemblies, provide single or dual channel ac and dc volts, amps, and watts, offsettable
and nonsinusoidal waveforms, duty cycle, thermocouple measuring and sourcing, internal
calibration and diagnostics, and digital control over all the analog assemblies.
DACS are used to control the level of dc signals and to control the amplitude of ac
signals.
+ _
SCOM
Figure 2-3. Synthesized Capacitance Function
C
ref
K
DAC
-1
C = (1 + K) • C
x
Theory of Operation

DDS Assembly (A6)

ref
yg118f.eps
2
2-5