Protek 9216A, Руководство пользователя, Страница: 19 / 77

18
Null Calibration Procedure
Whenever the test configuration is changed, including a change of the fixture,
open and short circuit “null” calibrations should be made prior to taking
measurements to compensate for stray impedances, such as component lead
impedance, and fixture, cable and other stray capacitance. Null calibration should
be performed after any change in fixture configuration or for changes in the drive
amplitude. This calibration corrects for all frequencies and all ranges-it is not
necessary to re-calibrate for changes in frequency. For critical measurements,
null calibration should be performed frequently at some interval during the course
of measurements.
The LCR meter store open and short circuit calibration data in nonvolatile
memory. These data values are stored with the STO key and recalled using the
RCL key, allowing null calibration data to be saved for different fixtures.
The null calibration procedure is on the menu that is invoked by pressing the
CAL (Calibrate) key in the SETUP group of keys on the front panel of the meter.
To perform a null calibration, press the CAL
key until the message “nuLL cAL”
appears on the alphanumeric display. Pressing the ENTER key while this
message is being displayed causes the message to change to “Short cAL.”
The short-circuit null calibration is done by placing a wire in the fixture
(thereby shorting the fixture’s terminals) that is between 26 to 16 AWG (0.02" to
0.05" or 0.51 to 1.30 mm dia.). The calibration proceeds automatically after the
user presses the
ENTER key and moves hands and any miscellaneous objects
away from the fixture. When the short circuit calibration is finished, the meter
prom
pts the user for the next operation by displaying the message “oPEn cAL.”
To perform the open-circuit null calibration, remove the shorting wire, press
ENTER and again move hands away from the fixture. When the unit has finished,
it displays the message “cAL donE.” To dismiss this message and return to a
normal display mode, press the
DISP (Display) key.
Changing Test Setup Parameter Settings
When powered on, the 9216A LCR Meter initially uses the default test setup
parameters, which include selection of the automatic (
AUTO ) measurement
mode, and the result of the measurement is displayed on the alphanumeric
readout. For most measurements, the test conditions in the automatic mode are
sufficient. However, by pressing the parameter keys on the front panel, the user
may enter customized test setup parameter selections, and by pressing the
keypad keys, enter the desired values of test parameters. Test parameters that
are not associated with dedicated keys on the front panel or keypad, such as the
number of measurements being averaged, deviation measurements, etc., may be
entered by pressing the
DISP key to enter the ENTRY mode. Table 3-1 below
shows appropriate settings for typical component values.