Operation 4–8
External bias allows an external DC power supply to be connected to the DUT via the Bias
terminals on the rear panel. If an accurate bias voltage is required, a DC voltmeter can be
connected between the RED Kelvin clip and ground (the crocodile clip). If using a 1EV1006
fixture, the DC voltmeter can be connected between the Bias terminal and the bar along which
the jaws slide. The bias voltage is routed via the ORANGE BNC connector. Take care that the
AC test voltage (Vac) present on the test leads does not affect the DC voltmeter accuracy. If
necessary, temporarily set Vac to a low value.
Sngl/Rep toggles between Single shot mode and Repetitive mode. Single shot mode is
indicated by the lack of a continuously flashing diamond (۞) in the top right corner of the
screen. Conversely, the presence of a continuously flashing diamond indicates that the
instrument is in repetitive mode. The asterisk flashes once every time the instrument makes a
measurement. Repeat Trigger cannot be used when External Control is set to GPIB or RS-
232.
When in single shot mode, the Trigger key initiates a single measurement.
Pressing Local restores control to the front panel when the instrument is under GPIB or RS-232
control.
4.2.7 The Data Entry Keypad
The data-entry keypad is a multi-function key set permitting manual entry of data values,
measurement units and control codes.
Terminate with Enter to accept the key sequence.
4.3 Trimming
The purpose of trimming is to eliminate the effects of stray capacitance or series impedance in
the connecting leads or fixture.
The trim values are held in non-volatile stores and for most measurements no retrimming is
necessary. The exceptions are when the lead set or fixture is changed or when the highest
possible accuracy is required for measurements of very high or very low impedances.
The instrument trims by making measurements at a number of frequencies and storing the
corrections for each. If the measurement frequency is changed the instrument automatically
applies a new correction value by interpolation of the stored values. Corrections for the Rdc
functions are also stored.
For O/C Trim the Kelvin clips or fixture jaws should be separated by a distance equivalent to
the DUT pin separation.
For S/C Trim the connector jaws should be clipped to a piece of wire or a component lead as
close together as possible. Do not connect the clips directly together: this does not provide the
necessary 4-terminal short circuit and will lead to trim errors.
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