4.13 Sourcing Functions (SMX2044)
The SMX2044 adds a number of sourcing functions, giving greater versatility for a variety of applications. All of
the available sources, VDC, VAC, IDC, are isolated (floating with respect to the chassis). This allows sourcing with
a significant common mode voltage as well as the ability to connect several SMX2044 units in parallel for increased
DC current, or in series for increased DC voltage.
Two digital-to-analog converters (DACs) are used for the source functions, a 12 bit DAC, and a Trim DAC. The
last augments the 12 bit DAC to form a 16 bit composite DAC and adds an additional 8 bits of resolution. For
functions requiring high precision, use both DACs by selecting the ClosedLoop mode, otherwise only the 12 bit
DAC is utilized. DCI source is limited to the 12 bit DAC only.
All three source functions use the
V,
Ω
+
, and the
V,
Ω
-
terminals of the SMX2044.
4.13.1 DC Voltage Source
The SMX2044 has a fully isolated bipolar DC voltage source. Two modes of operation are available: fast settling or
closed loop. In the Closedloop mode the DMM monitors the voltage source output, and updates it using the
composite 16 bit DAC, at a rate proportional to the set measurement rate. The closedloop mode offers the best
accuracy and resolution. A 10 rps or lower measurement rate is recommended for the Closedloop mode. In the fast
settling mode, no adjustments are made and the 12 bit DAC is used. Up to
±
10.0 V can be sourced, with 10 mA
maximum drive. The output source resistance of the DCV source is approximately 250
Ω
.
Figure 4-14. Sourcing DC voltage. The figure indicates the internal monitoring of the output in closed loop
operation.
39
Signametrics
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