The Model 72AD Capacitance Meter provides instant,
direct-reading, three-terminal and differential capacitance
measurements from 0.05 pF to 2000 pF. This capacitance
coverage is divided into four ranges, selected by panel
push-buttons or remotely. These are arranged in a 2, 20, 200
and 2000 pF full-scale sequence. (1) The digital display
provides 3 digits plus one readout, decimal point, and + or
- Indications. The solid-state design and the low-level
crystal-controlled signal source contribute to the high
stability and excellent reliability of the instrument.
The measurement of semiconductors Isfacilitated by the 15 mV
rms level of the 1 MHz test signal, and by the provision for
applying up to 600 volts of dc bias to the test specimen.
Bias voltage, of either polarity, may be applied to either
or both sides of the specimen .
The Model 72AD employs an unusual range-switching system
using switching diodes and miniature reed relays; the
elimination of the switch contacts from the measurement
circuits assures a maximum of reliability and stability. The
phase-sensitive detection system permits the measurement of
even low-Q devices (down to Q =1) without sensibly degrading
the accuracy of the measurement.
Two plug-in test connection adapters are supplied with the
Mode! 72AD. One of these, fitted with two sets of coaxial
connectors, Is Intended for use with coaxial cables and
remotely located test fixtures for both three-terminal and
differential measurements. The other adapter, with two
terminal posts, is used for wire-lead type components;
differential measurements are not possible with this adapter.
Both linear dc and binary coded decimal outputs are
available at rear-pane! terminals and at the appropriate
pins on the rear edge connector. These two features extend
the range of applications beyond ordinary laboratory
measurements to include production testing and integration
into a controlled test system, using logic-level programming.
Remote ranging is controlled by grounding the EXT PROG
terminal on the rear edge connector, disabling the
front-panel range switches. Grounding anyone of the four
range- line terminals will then select that range.
Connection to the edge connector should be made with an
Amphenol Type 225-22221-1 01 plug, or equivalent.