Voltage-Mode, Current Mode
The VI measurement setting allows one to set the measurement mode. In Voltage mode, the instrument adjusts
the terminal voltage and measures the current. In current mode, the instrument adjusts the current and measures
voltage. For example, in a diode-like device, when measured by voltage mode the current increases very rapidly
after the device threshold is reached. It’s much more controllable to operate the in current mode, ie, adjust the
measurement current and report the device voltage
Control Settings
These entry boxes set the parameters for a measurement. Move the cursor to the entry box and left click to place
the cursor in the entry box. Then edit the value. Carriage return is not required. When you click on START,
the instrument software will read the values in these boxes. Usually some experimentation is required to get the
desired curve.
Curve Data
This section of the control panel logs the measured values as they are completed. The ’Save CSV’ function (see
above) copies this data to a
.CSV
file.
Measurement Cursors
Figure 3: Cursors
A left click in the plot area deposits a measurement point and shows the coordinates of that point.
A second left click deposits a second point, which shows the coordinates of that point. The second point also
generates a line between the two points, a readout of the slope, and a readout of the inverse of the slope. This
provides a semi-automatic method of determining incremental conductance and resistance.
For example, in figure 3 the operator has deposited two measurement points on one of the collector character-
istic curves. The collector incremental resistance is 420 ohms. This is useful information for building a model of
the transistor for circuit analysis or simulation.
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