Agilent Technologies 4294A, Programming Manual

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64 Chapter 4
Preparing For Accurate Measurement
Fixture Compensation
Example 4-3 shows a sample program for measuring data to be used for calculating a
fixture compensation coefficient. This program is given the file name com_meas.bas and is
stored on the sample program disk.
Enter standard values for open data, short data and load data. This program then measures
open data, short data and load data at fixed measurement points preset by the Agilent
4294A and stores the measured data and the defined standard values in a flash disk
(nonvolatile memory disk) by giving the data the filenames COM_DATA and STD_VAL,
respectively.
Lines 60 to 150 These lines distinguish between the external controller and Instrument
BASIC and set the GPIB address and select code. In the case of
Instrument BASIC, flash memory is used as the storage unit.
Lines 160 to 180 These lines substitute the selection of data measurement points to the
variable Cal_point$, the name of the file to be retained measured data
to the variable File$, and the name of the file to be retained as standard
value to the variable Std_file$.
Lines 220 to 250 These lines reset the Agilent 4294A and then substitutes the data
measurement points to Cal_point$.
Lines 290 to 340 These lines use the subprogram Inp_data to acquire standard values to
enter open data, short data and load data.
Lines 350 to 400 These lines set the standard values. The open standard capacitance
needs to be in femtofarad, so these lines make the necessary
conversion.
Lines 440 to 450 These lines set 1 to Bit 8 of the instrument event status register (the bit
for the completion of the measurement of calibration data and
compensation data) and to Bit 2 of the service request enable register
so that SRQ can be used.
Lines 470 to 540 These lines measure open data, short data and load data by using the
subprogram FNFixt_comp. If an error is detected after any
measurement, the program is terminated.
Lines 580 to 740 These lines select the IEEE 64-bit floating-point format for the data
transfer format, read open data, short data and load data to store them
in the arrays Com_o(*), Com_s(*), and Com_l(*), respectively.
Lines 790 to 810 These lines delete a file named File$ if already exists.
Lines 830 to 860 This lines create a file named File$ and write the data stored in the
arrays Com_o(*), Com_s(*), Com_l(*) to that file.
Lines 880 to 900 These lines delete a file named Std_file$ if already exists.
Lines 910 to 950 This lines create a file named File$ and write the open/short/load
standard values.
Lines 970 to 980 These lines indicate the message of completion and terminate the
program.
The following describes FNFixt_comp, a data measurement subprogram for fixture
compensation, which is shown in lines 1020 to 1280.
Line 1050 This line clears the status byte register.
Lines 1060 to 1070 These lines prompt the connection for the measurement specified by