Operator`s manual

Exam
ple Two: Defects in coils, inductors, or transformers can be manifested as an increased decay, or
greatly attenuated resonance when stimulated with a charged capacitor. The Totalizer function can be
utilized to count transitions above a preset Threshold voltage as in the Figure 4-14 below.
Figure 4-18. Testing inductor Q by counting the number of transitions of decaying resonance.
It should be taken in considerations that the signal being measured is AC coupled. This means that the
wave shape and its duty cycle can affect the DC average of the signal, and the effective value of the
threshold DAC which is being utilized. See section 4.15.1 (Threshold DAC) and figure 4.15 for details.
4.16 Source Functions (2064)
The SMU2064 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 PC
chassis). This allows sourcing with a significant common mode voltage as well as the ability to connect
several SMU2064 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,+, and the V,- terminals of the SMU2064.
4.16.1 DC Voltage Source
The SMU2064 has a fully isolated bipolar DC voltage source with span of -10V to +10V. Its current
output is limited to about 5mA, and it has a source impedance of about 120. This source is very fast,
setteling in less than 10µs. Its resolution is 12 bits or about 5mV. For a more accurate DCV source, select
the Closed-Loop mode. Int this mode the aplitude is monitored and adjusted using an additional DAC
(trim dac) resulting in 18 bits of resolution. It is necessary to perform repetitive measurements while in
this mode. Use DMMRead or DMMReadNorm to allow the DMM to make the adjustments. The trade
off is setteling time, which is reduced to a couple of seconds. Use an Aperture of 160ms or higher when in
the Closed-Loop mode. Maximum drive of the VDC source is 10 mA. The output source resistance of the
DCV source is approximately 220 . The source voltage is available at V,2+ and V,2- terminals.
It is possible to improves the voltage accuracy delivered to the load by use of a Kelvin connection. This
eliminates the effect of the source lead wires resistance. To do this, connect the I,4+ and I,4- terminals
to the load and use DMMReadHiLoSense to monitor the voltage level at the load. Read about this
measurement function it in section 4.19.
4.16.2 Source DC Voltage and measure DC Current
Select this function by using DMMSetFunction(nDmm, SrceV_MsrI). While in this function, perform
open calibration using DMMOpenTerminalCal(), which calibrates the source resistance. Set the voltage
using DMMSetDCVSource(). Repeat the DMMSetDCVSouce() for at least five times in order to arrive
at the correct voltage. Using DMMRead() or DMMReadNorm() will read the DC current through the
load. The Voltage can be set from 0 to +/-10.0V, but the available current is limited depending on the set
voltage, as depicted in figure 4-20 below. It is necessary to repeat both DMMRead() and
Signametrics 54