Operator`s manual

Figure 4-5. Leakage Test Configuration. Measurement of reverse diode leakage at 5V.
4.3.6 Extended Resistance Measurements (SM2044)
The Extended Resistance measurement function operates as complement of the standard resistance measurement.
t, this function forces specified 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 a onnection diagram in Figure 4-6. Enter the
X
*
stor
pressed as V
L
(1+R
S
/R
L
) < 10.2V. Use the DMMSetExternalShunt() to
e test voltage (the voltage
e of high value and vise versa.
T tion fo h va lem bl ers, and other leaky objects
such as printe bo nnectors and semiconduc
As an example, consider a 1.0MΩ shunt and a 4V test voltage. In this case, the lowest resistor one can measure will
be 1.2122MΩ n V
S
is at ere sin MΩ * 4V / 1.2122MΩ = 3.3V which is the limit for
V
ur e l ched w
L
is set to 8.5V and the measured resistance falls below 5.001MΩ
si (1 Ω/5 Ω = 10.2
Where the last forces a predefined curren
m
n external sense resistor. To perform this measurement use the c
value of the sense resistor R
S
using DMMSetExternalShunt(), and set the test voltage with
DMMSetDCVSource(). Due to the availability of a much higher test voltage than the normal resistance function,
this function is fit for very high value resistance measurements. On the other hand, the ability to set to some low
voltages is significant in applications where specific test voltage is required 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 is
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
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 resi
alue. The source voltage limit may be exv
set the value of the external shunt being used. Use the DMMSetDCVSource() to set th
across the resistor being measured). For high value resistances, the shunt should b
his func is useful r testing hig lue resistive e ents such as ca es, transform
d circuit ards, co tors.
. The shu t voltage
its limit h ce 1.0
S
. The so ce voltag imit is rea
)
hen V
nce 8.5V + 1.0M .001M V.
Signametrics 30