Table of Contents
Advertisement
CHAPTER
I
GENERAL DESCRIPTION
1 .1
GENERAL.
The Direct Capacitance Bridge, Model 75D, (1 MHz) is a self-
contained test instrument ( Figure 1 ) designed for use as a precision laboratory bridge
to measure values of capacitors, inductors, and semiconductor devices, or to perform
single-limit sorting tests of capacitive or inductive specimens,,
The instrument provides direct (3-terminal ) readings of parallel capacitance (C),
effective parallel conductance (G), and equivalent parallel resistance (Rp).
Parallel
inductance (L) is measured in terms of equivalent capacitance, and dissipation (D) or
Q are readily determined by a simple computation.
The Model 75D is largely insensitive to capacitdnce from either side of the specimen
to ground and provides accurate readings even in the presence of relatively large stray
capacitance,,
Thus, the direct capacitance of specimens is precisely measured, and a
remote test jig or coaxial cables may be used to connect specimens without introducing
errors due to jig capacitance or cable capacitance.
Test specimens may be biased
directly by the internal dc supply, or an external bias voltage may be applied through
terminals on the front panel.
External capacitance standards also may be connected at
the front panel to check calibration or to perform comparison or differential measurements.
Other typical uses of the Model 75D are as follows:
Measurement of the capacitance of semiconductors
Measurement of the capacitance of varactors
Test or measurement of capacitance elements of microcircuit chips
Measurement of the temperature coefficient of capacitors.
Measurement of stray circuit capacitance.
Measurement of stray circuit capacitance
In addition, the Model 75D is
used for single-limit and dual-limit testing and sorting
operations of capacitors, inductors, and semiconductor devices during production testing,
incoming inspection, quality assurance, and similar applications.
1 .2 EQUIPMENT DESCRIPTION „
The M odel 75D contains, in one cabinet, abridge,
signal source, null detector, power supply and bias supply.
All operating controls and
indicators are mounted on the front panel.
If required, the Model 75D may be removed
from the cabinet and installed in a standard 19-inch rack.
A bracket is installed on the rear panel to secure the instrument's ac power cable,
and a terminal shield is provided for the TEST binding posts.
This serves to shield the
binding posts from hand-capacitance or stray-capacitance effects when the REMOTE
coaxial terminals are used to connect specimens of standards.
75D
b-370
1
Advertisement
Table of Contents
