Specifications

Figure 4-5. Leakage Test Configuration. Measurement of reverse diode leakage at 3.3V.
4.3.6 Extended Resistance Measurements (SMX2044)
The Extended Resistance measurement funct
here the last forces a predefined current, this function forces sp
ion operates as complement of the standard resistance measurement.
ecified voltage. Where the normal resistance
easurement is limited to pre defined current sources, this function has a variable voltage, and it limits current flow
by an external sense resistor. To perform this measurement use the connection diagram in Figure 4-6. Enter the
MSetExternalShunt(), and set the test voltage with
ailability of a much higher test voltage than the normal resistance function,
is he other hand, the ability to set to some low
s
rsa.
ers, and other leaky objects
As an examp er unt ol e, the lowest resistor one can measure will
be 1.2122MΩ un V
S
is at ere sin * 4V / = 3.3V which is the limit for
V
our ge l ched w set to 8 e measured resistance falls below 5.001MΩ
si (1 Ω/5 ) = 10.2
W
m
value of the sense resistor R
S
using DM
MMSetDCVSource(). Due to the avD
th function is fit for very high value resistance measurements. On t
ages is significant in applications where specific test voltage is revolt quired such as to prevent semiconductor’s
turn-on, or prevent sensitive sensors’ damage due to access voltage or current. The DMM compensates for the
voltage drop across the sense resistor as to provide the specified test voltage. Each time the DMM makes a
measurement using DMMRead(), DMMReadStr() or the DMMReadNorm, it adjusts the test voltage. There are
several limitations that should be considered while using this function. The internal voltage source of the SM2044 i
limited to about +/-10.2V. Therefore the sum of the voltages across the sense resistor and the measured resistor is
limited to this amount. Also the maximum voltage allowed across the sense resistor is limited to 3.3V. Exceeding
either value will result in Over Range reading. The limit imposed by the shunt resistor may be expressed as V
L
/R
X
*
R
S
< 3.3V, where V
L
is the test voltage, R
X
is the resistance being measured, and R
S
is the external sense resistor
value. The source voltage limit may be expressed as V
L
(1+R
S
/R
L
) < 10.2V. Use the DMMSetExternalShunt() to
set the value of the external shunt being used. Use the DMMSetDCVSource() to set the test voltage (the voltage
across the resistor being measured). For high value resistances, the shunt should be of high value and vise ve
This function is useful for testing high value resistive elements such as cables, transform
such as printed circuit boards, connectors and semiconductors.
le, consid a 1.0MΩ sh and a 4V test v tage. In this cas
. The sh t voltage
its limit h ce 1.0MΩ 1.2122MΩ
S
. The s ce volta imit is rea hen V
L
is .5V and th
nce 8.5V + 1.0M .001MΩ V.
Signametrics 30
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