GLK INSTRUMENTS
Rev. 3.3, 21 January 2007
Copyright 2007
5
V. DESCRIPTION
The Model 3000 Digital Capacitance Meter is the first commercially available low
cost, high accuracy instrument designed ex clusively for the measurement of very
small value capac itors and capacitors wh ose size and shape are not conveniently
handled by conventional sock ets, clamp fixtures, or alligator clip lea ds. This
instrument is particularly useful f or the measurement chip capacit ors whose small
size precludes the use of identifying marks.
The Model 3000 em ploys a unique and pat ented (U.S. Patent No. 4806846)
switched capacitor circuit and a ratio metric measurement technique that eliminates
errors due to stray capacitance t o ground. The patent ed circuit has high common-
mode rejection and eliminates errors due to changes in the refe rence voltage from
temperature, aging, etc. This unique circuit allows the capacitor under measurement
to be remotely connected to the meter via two, miniature, shielded probes or coaxial
cables without affecting the accuracy or resolution of the instrument.
The convenience of using miniature pr obes solves the costly problem of
constructing special t est fixtures and shie lded boxes for the determination of the
capacitance of a vari ety of objects. For example, the Model 3000 with its standard
probes can easily determine the capac itance between the pins of a connector, the
large signal gate capacitanc e of power MOSFETs, the depletion capacitance of
diodes, the capac itance between the traces on a printed circui t board, or even the
static capacitance of microstrip or stripline microwave circ uits. Using ultra-miniature,
shielded probes, very accurate wafer le vel, large signal meas urements of MOS
capacitors are easily obtained.
Miniature, shielded probes are normally supplied with the instrument; however,
the Model 3000, due to its unique c ircuitry, can acc ommodate a large v ariety of
custom built shielded probes, special shielded connectors, or test fixtures. Coarse
and fine of fset adjustment potentiometers are provided on the front panel of the
instrument to compensate for any unshield ed test fixture capacitance up to 1.5 pF.
Capacitors can be remotely connected to the Model 3000 usin g standard coaxial
cables such as RG-223. The Model 3000 maintains its accuracy and resolution wit h
or without probes.
Auxiliary analog outputs of the meter reading (0-200mV ) and reference voltage
(5.000V) are available on the bac k panel. These outputs can be c onnected to digital
voltmeters, plotters, data loggers, comput er data acquisition s ystems, etc. using
standard banana jacks and shielded coaxial cables.
Fully isolated digital I/O is available at the USB port on all new instruments
starting at serial num bers 30024 and up. Older instruments can be upgr aded to
support digital I/O fo r a nominal charge. Contact GLK Instruments for details. The
USB port provides access to the instrum ent’s 24-bit ADC an d range switches.
