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Impedance Measurements of Magnetic Heads
using Constant Current in Production and
Quality Control Departments
Application Note 369-3
HP 4284A Precision LCR Meter

Introduction 2. GO/NO-GO Testing of Several Frequency Points

Measuring the impedance of a magnetic head is a The List Sweep function3 allows sweeping of any of
valuable technique for checking its quality. This type 10 frequencies. Since it is possible to limit the
of measurement involves the following difficulties measurement value per frequency, GO/NO-GO
and demands. testing of constant current measurements can easily
be performed at several frequencies.
It must be possible to conduct constant current
measurements at a number of frequency points, 3. A Memory Card Allows for Easy Setups
not only in the development department, but also
in the production and quality control departments A maximum of ten instrument settings for
as well. It should also be easy to change from one measurement conditions can be recorded on a single
set of measurement conditions to another when memory card. By preparing measurement conditions
testing different devices. for different samples it is easy to go from one type of
measurement to another without making mistakes.
The additional errors caused by test fixtures,
measurement cables, and the like prevent reliable 4. A Powerful Error Compensation Function
measurements. These types of errors must be Reduces the Additional Errors Caused by
minimized. Test Fixtures, and Measurement Cables

Discrepancies between measurement values of This function minimizes the influence of test fixtures
different channels when a scanner is used must be on the test results.
able to be compensated for.
5. Multi-Channel Compensation Minimizes
Conventional instruments cannot meet these demands. Discrepancies Between Scanner Channels

Solutions Offered by the HP 4284A The use of a scanner interface4 compensates for
channel discrepancies for up to a maximum of 128
1. Easy Constant Current Measurements channels. This function prevents discrepancies in
measurement values between different channels,
The ALC1 function allows easy constant current and ensures stable measurements.
measurements within a range of 100