Agilent Technologies 4156b, User Manual

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Agilent 4155B/4156B User’s Guide Vol.2, Edition 5 7-5
Data Variable and Analysis Function
Data Variable
User Function
A user function consists of one or more data variables used in an expression. You
define the user function name, expression, and unit on the CHANNELS: USER
FUNCTION DEFINITION screen.
You can use a user function inside another user function. And you can set up the
user function on the DISPLAY: DISPLAY SETUP screens to plot the user function
values or display the numeric value.
To define a user function, you define a name and an expression on the CHANNELS:
USER FUNCTION DEFINITION screen. If desired, you can define a unit, such as
ms.
• User function name must start with alphabet character and can consist of
maximum six alphanumeric characters. Name must be unique. Name is case
sensitive. For example, Gm is different from gm.
• Unit name is optional. Length: 1 to 6 characters. Valid characters: any
characters.
For the syntax of an expression, refer to “Expression” on page 7-8.
Example
To define a user function for mutual conductance gm of an FET, define gm on the
CHANNELS: USER FUNCTION DEFINITION screen as follows:
NAME UNIT DEFINITION
gm S DELTA(Id)/DELTA(Vg)