Operator`s manual

43 Signametrics
s
s are
stimulate a dV/dt across the capacitor. Use short high quality shielded probe cables with no more than
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.
cal.
urces such as computer monitors. For best measurement accuracy at low capacitance values, zero the DMM using
-12
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.
Applications include I/V characteristics of Diodes, LEDs, Low voltage Zener diodes, Band Gap devices, as well a
IC testing and polarity checking. Typical current level uncertainty for diode measurements is 1%, and typical
voltage uncertainty is 0.02%.
4.9 Capacitance Measurement (SM2064)
The SM2064 measure capacitance using a differential charge balance (ramp) method, where variable current
utilized to
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 Auto ranging function may not be practi
Because Capacitance measurement is sensitive to noise, you should keep the measurement leads away from noise
so
the ‘Relative’ while in the 10 ηF range. The effect of the cable quality and its total capacitance is profound
particularly on low value capacitance. For testing surface mount parts, use the optional Signametrics SMT Tweeter
probes. You may increase the measurement speed by using the DMMSetCapsAveSamp() function. See figure 4
for connection.
Figure 4-12. Measuring capacitors or inductors is best handled with coaxial or shielded probe wires.
4.10 I
second
n-Circuit Capacitance Measurement (SM2064)
method provided for measuring capacitors is the AC based method. Though not as accurate as the above
nc mulus is set at 0.45V peak, which is lower than a
t
the AC source signal. This open Calibration operation must be performed with the measurement cable or probes
A
fu tion, the advantage of this method is that the default sti
iconductor junction on voltage. It may also be set over sem a wide range of voltages. A further advantage is the
ability of this function to measure capacitors that have a very low value parallel resistance, which is impossible to
do using conventional methods. This test function operates by figuring the complex impedance and extracting from
it both, the capacitance and resistance. The measurement is practical down to a few hundred Pico Farads, and up to
several thousands micro Farads, with parallel resistances as low as 20Ω to 300Ω depending on range. Once set to
this function, use DMMRead(), DMMReadStr() and DMMReadNorm() to measure the capacitance value. To ge
the resistance value use DMMGetACCapsResist() following a read. Each of the ranges must be calibrated with
open terminals prior to making measurements. Each range must be calibrated. Do this by activating the AC-Caps
function, selecting the range to be calibrated and issuing DMMOpenCalACCaps(). The last function normalizes