Keithley 2606B System SourceMeter, Справочное руководство, Страница: 185 / 756

In this section:
Analog-to-digital converter ....................................................... 4-1
Source-measure concepts ....................................................... 4-1
Measurement settling time considerations ............................. 4-18
Effects of load on current source settling time ........................ 4-19
Creating pulses with the 2606B .............................................. 4-19
Analog-to-digital converter
The 2606B SMUs have an integrating analog-to-digital converter (ADC). The integrating ADC uses a
ratiometric analog-to-digital conversion technique. Depending on the configuration of the integrating
ADC, periodic fresh reference measurements are required to minimize drift. The measurement
aperture is used to determine the time interval between these measurement updates. For additional
information, see
Autozero (on page 2-37). To help optimize operation of this ADC, the instrument
caches the reference and zero values for up to ten of the most recent number of power line cycles.
For additional information, see
NPLC caching (on page 2-39).
Source-measure concepts
This section provides detailed information about source-measure concepts, including:
•
Limit principles (on page 4-1)
•
Overheating protection (on page 4-2)
•
Operating boundaries (on page 4-3)
•
Basic circuit configurations (on page 4-12)
•
Guard (on page 4-16)
Limit principles
A limit acts as a clamp. If the output reaches the limit value, the System SourceMeter
®
instrument
attempts to prevent the output from exceeding that value. This action implies that the source will
switch from a V-source to an I-source (or from an I-source to a V-source) when a limit is reached.
As an example, assume the following:
System SourceMeter
®
instrument: V
SRC
= 10 V; I
LIMIT
= 10 mA
Device under test (DUT) resistance: 10 Ω
With a source voltage of 10
V and a DUT resistance of 10 Ω, the current through the DUT should be:
10 V / 10
Ω = 1 A. However, because the limit is set to 10 mA, the current will not exceed that value,
and the voltage across the resistance is limited to 100 mV. In effect, the 10 V voltage source is
transformed into a 10 mA current source.
The 2606B output does not exceed the compliance limit, except for the compliance limit conditions
described in
Source-measure capabilities (on page 2-35).
Section 4
Theory of operation