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Agilent AN 1305-4
Effective Electrolytic Capacitors Testing
Application Note
Agilent 4263B LCR Meter
Introduction (4) When a shorted device is measured, Agilent 4263B LCR Meter Solution
With increased requirements for size the internal circuit of a conventional (1) Accurate Low Impedance Measurement
reduction and higher reliability design, LCR meter is latched up, and it needs The 4263B LCR Meter employs a
it is becoming necessary to evaluate a long recovery time. 4-terminal pair configuration and an
electrolytic capacitors employed in advanced low noise design so that it
electronic equipment. Production vol- (5) Some inexpensive LCR meters do makes accurate measurements up to
ume has been increasing for circuit not range up to 100 kHz, and the 1 F. For example, when 10 mF is meas-
applications. Manufacturing and QA equivalent series resistance of the ured at 120 Hz, the 4263B's accuracy,
now have to improve their testing of electrolytic capacitors need to be 0.57% can be achieved. Also, the meas-
electrolytic capacitors. Here are the evaluated at 100 kHz. urement cable can be extended up to
solutions offered by the Agilent 4 m while maintaining the measurement
4263B LCR Meter to meet these meas- (6) Most LCR meters cannot detect accuracy.
urement requirements. whether or not the contact between
the fixture's electrodes and the device's (2) High System Throughput
electrode is good, thus decreasing the The measurement speed of the 4263B
Current Problems in Electrolytic reliability of a measurement. LCR Meter at 100 Hz/120 Hz is 25 ms
Capacitor Evaluation (Meas.Time: SHORT). Figure 1 shows
When making electrolytic capacitor (7) There are no test fixtures for the you the fluctuation of the 22 mF
measurements using conventional terminals (for example, big screw Aluminum Electrolytic Capacitor
LCR meters, there are quite a few electrodes) of the big electrolytic Measurement by SHORT mode, and
shortcomings. capacitors. 120 Hz of the 4263B.
(1) Impedance value of the electrolytic
capacitors is usually so low that an
accurate measurement is hard to
achieve. Some LCR meters cannot
measure above 20 mF due to a limited
measurement range.
(2) Electrolytic capacitors are cur-
rently tested at 100 Hz or 120 Hz. The
measurement speed at those frequen-
cies is quite slow, and higher through-
put cannot be achieved by automatic
measurement systems.
(3) When a charged capacitor is con-
nected to the measurement terminals
of the LCR meters, the circuit is easi-
ly damaged by the discharge energy.
Figure 1. Fluctuation of the measurement value at SHORT
2
In addition, the 4263B has the follow- (7) Various Test Fixtures
ing features which allow easy system The Agilent 16089A Kelvin Clip Leads
integration, and improve measurement have two large clips that can accept
throughput. device electrodes with a diameter of
15 mm. Figure 3 shows a big capacitor