Operator`s manual

the accuracy and stability of the DMM. It also allows monitoring of the PC internal temperature, which is important
for checking other instruments in a PC-based test system.
4.6 Diode Characterization
33 Signametrics
pplications include I/V characteristics of Diodes, LEDs, Low voltage Zener diodes, Band Gap devices, as well as
.7 Capacitance Measurement (SM2042, SM2044)
where variable currents
n
tical.
to noise, you should keep the measurement leads away from noise
urces such as computer monitors. For best measurement accuracy at low capacitance values, zero the DMM using
. The effect of the cable quality and its total capacitance is profound
ter
4-9
The Diode measurement function is used for characterizing semiconductor part types. This function is designed to
display a semiconductor device’s forward or reverse voltage. The DMM measures diode voltage at a selected
current. The available source currents for diode I/V characterization include five DC current values, 100 ηA, 1 µA,
10 µA, 100 µA and 1 mA. The SM2042 and SM2044 have an additional 10 mA range. The SM2044 also has a
variable current source that can be used concurrently with DCV measurement (see “Source Current / Measure
Voltage”). This allows a variable current from 10 ηA to 12.5 mA. The maximum diode voltage compliance is
approximately4 V.
A
IC testing and polarity checking. Typical current level uncertainty for diode measurements is 1%, and typical
voltage uncertainty is 0.02%.
4
The SM2042 and SM2044 measure capacitance using a differential charge balance method,
are utilized to produce a dv/dt across the capacitor. Use short high quality shielded probe cables with no more tha
200 pF. With the exception of the 10 ηF range, each of the ranges has a reading span from 5% of range to full scale.
Capacitance values less than 5% of the selected range indicate zero. Since some large value electrolytic capacitors
have significant inductance, as well as leakage and series resistance, the Autoranging function may not be prac
ecause Capacitance measurement is sensitiveB
so
the ‘Relative’ while in the 10 ηF range
particularly on low value capacitance. For testing surface mount parts, use the optional Signametrics SMT Twee
probes. You may increase the measurement speed by using the DMMSetCapsAveSamp() function. See figure
for connection.
F igure 4-9. Measuring capacitors or inductors is best handled with coaxial or shielded probe wires.
ages. A further advantage is the
4.8 In-Circuit Capacitance Measurement (SM2044)
A second method provided for measuring capacitors is the AC based method. Though not as accurate as the above
function, the advantage of this method is that the default stimulus is set at 0.45V peak, which is lower than a
semiconductor junction on voltage. It may also be set over a wide range of volt