Operator`s manual

Figure 4-15. Sourcing DC current and measuring voltage in the two-wire configuration. This function can
Synthesizing Resistance (SM2044)
thod, e DMM to
or hesizing resistance, the readings return the measured value.
which sistanc is synth ion
vider type load, as in a v rs
, it is
pliance limit of 2.5V. This means that the DMM current source does not behave as a current
urce when the voltage at its terminals is allowed to exceed 2.5V. Therefore synthesizing a resistance value
nction with all
s the external resistor.
t
be used for semiconductor parametric tests.
4.14
T 044 synthesizes resistance using an iterative me which requires repeated
rections to the synthesized value. While in synt
he SM2 reading of th
make c
There are two basic circuit types into re e esized; current source, such as the resistance funct
esistoof another Multimeter, and voltage di oltage divider circuit, where one of the two r
ein the network is being synthesized as in Figure 4-16. When synthesizing a resistance into a current sourc
important to consider its compliance voltage limits. For instance, a DMM’s 20k Ohms range will typically sources
100uA, and have a com
so
greater than 25kΩ (2.5V/100uA) will result in the SM2044 indicating an unstable reading.
For improved accuracy, perform open terminal calibration by using the DMMOpenTerminalCal() fu
terminals are open.
The following are limits that must be observed while synthesizing resistances:
Limitations synthesizing into current source:
1) The maximum load current, I
S
, is 10mA or 3.3/R
S
whichever is smaller. R
S
i
2) The maximum value that can be synthesized is 6.7/I
S
– 220 or V
C
/I
S
, whichever is smaller. V
C
is the curren
source compliance voltage.
3) Resistance settings resolution equals 0.1mV/ I
S.
This means that with a source current of 1uA the resolution
is 100Ω.
Limitations synthesizing into a voltage divider:
1) The maximum current the SM2044 can provide to the load is 10mA or 3.3/R
S
, or (10 – V
x
) / (R
x
+ R
s
+
220), whichever is smaller. R
S
is the external resistor.
2) The approximate value that can be synthesized is between 0.1 * R
s
to about 100 * R
s
Signametrics 40