3156B User Manual
Racal Instrument © 2005
Programming Reference 5-107
Parameters
Name
Variable
Type
Description
instrHandle
ViSession
The Instrument Handle is used to identify the unique
session or communication channel between the driver
and the instrument. If more than one instrument of the
model type is used, this will be used to differentiate
between them. Note that the initialize function may be
used to associate multiple instrument handles with a
single instrument.
FMArbModulationSCLK
ViReal64
Programs the sample clock for the arbitrary modulating
signal.
Valid Range: 1 to 5e6 (S/s)
Default Value: 1e6
Return Values
Displays the return status of the function call. If the function was successful, it will return a status of
VI_SUCCESS, otherwise it will return an error code. Passing the error code into the function
"ri3156B_error_message()" will return a string describing the error.
Ri3156b_load_arb_FM_mod_data
Description
This command will download FM modulating waveform data to the arbitrary FM memory. Below you can see
how such data array is constructed. Downloading data to the arbitrary FM waveform memory is very different
than loading arbitrary waveform data. Waveform data programs amplitude domain therefore, every point
programs an amplitude level. On the other hand, FM modulating waveform data programs frequency domain
therefore, every point sets different sample clock frequency.
Arbitrary FM waveform sample file. This file has 80 frequency points of that will create the following output
modulation:
1. Stable 1MHz signal for 11 arbitrary FM SCLK intervals,
2. Sine shaped waveform, minimum frequency is 900047Hz and maximum frequency is 1.006Hz
3. Stable 1MHz signal for 19 arbitrary FM SCLK intervals.
The frequency of the modulating signal is computed from the following equation:
Modulation frequency = FM modulation SCLK / Number of Points in the arbitrary modulating waveform
The modulating waveform sample clock is programmed using the ri3156B_set_arb_FM_mod_sclk
Channel Dependency: Independent
