Figure 4-21. Connection topology, and symbolic diagram of the V-source/I-measure function.
4.16.3 AC Voltage Source
The AC voltage source is fully isolated. Both amplitude and frequency can be set. The frequency range is
10 Hz to 200kHz with 2mHz frequency resolution. The amplitude can be set from 30mV RMS to 7.2V
RMS by selecting one of two ranges. The source voltage and frequency settle in less than 10µs and its
amplitude setting provides 12 bits of resolution, or about 5mV steps. In the Closed-Loop mode of
operation the amplitude is monitor and adjusted while measurements are made, achving an effective
resolution of 18 bits or less than 200µV. In this mode it is necessary to perform measurements using
D
MMRead
or
DMMReadNorm
. This result is a very accurate output but a much longer setteling time of
about 2s. While in the Closed-Loop mode the Aperture should be set to a value that is higher than 160ms.
The maximum peak current is 10 mA. The source impedance is approximately 120
. The source voltage
is available at V,2
Ω
+ and V,2
Ω
- terminals.
4.16.4 DC Current Source
The SMU2064 has a fully isolated unipolar DC current source with five ranges. It uses the internal DAC
to control current level. This source function is useful for parametric component measurements as well as
for system verification and calibration, where a precise DC current is necessary to calibrate current
sensing components. Use the
DMMSetDCISource
to set the value of the current.
For improved resolution of the current source, use the Trim DAC. It has to be set separately, since it is
not included in the calibration record, or the control software. Use DMMSetTrimDAC() command with a
parameter of 0 to 100. Further details are in section 6.
When in OPEN_LOOP (see
DMMSetSourceMode()
), the voltage generated by the current source is
measured at the source terminals (upper two terminals). When set to CLOSED_LOOP the voltage is
measured by the sense terminals (lower two terminals) of the DMM, allowing remote voltage sense. The
last provides a true 4-Wire voltage sensing at the load, which improves accuracy by eliminating the effect
of lead wires. The source current is available at V,2
Ω
+ and V,2
Ω
- terminals.
Signametrics
56
