Compliance Principles - Keithley 6430 Instruction Manual

5-4 Source-Measure Concepts

Compliance principles

Compliance acts as a clamp. If the output reaches the compliance value, the SourceMeter
will attempt 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 in compli-
ance. The clamping value is determined either by a user-defined value (compliance setting) or
the measurement range (range compliance) since the unit will not output more than it is config-
ured to measure.
As an example, assume the following:
SourceMeter: V
DUT resistance: 1Ω
With a source voltage of 10V and a DUT resistance of 1Ω, the current through the DUT
should be: 10V/1Ω = 10A. However, because the compliance is set to 10mA, the current will
not exceed that value, and the voltage across the resistance is limited to 10mV. In effect, the
10V voltage source is transformed into a 10mA current source with a 10mV compliance value.
Determining compliance limit
The relationships to determine which compliance is in effect are summarized as follows:
•
•
The compliance that is in effect can be determined by comparing the displayed compliance
setting to the present measurement range. Make sure the correct measurement function is dis-
played. If sourcing voltage, select the current measurement function. Conversely, if sourcing
current, select the voltage measurement function.
If the compliance setting is lower than the maximum compliance value on the present fixed
measurement range, then the compliance setting is the compliance limit. If the compliance set-
ting is higher than the measurement range, then the maximum compliance value on that mea-
surement range is the compliance limit.
Table 5-2 provides examples for determining the actual compliance limit. For the first three
entries in the table, the compliance setting is 150V. On the 200V measurement range, the actual
compliance is 150V (compliance setting < measure range = real compliance). On the 20V and
200mV measurement ranges, compliance is 21V and 210mV, respectively (measure range
< compliance setting = range compliance). The same rules apply for the next three entries for
current compliance.
= 10V; I
SRC CMPL
Compliance Setting < Measurement Range = Real Compliance
Measurement Range < Compliance Setting = Range Compliance
= 10mA