Chapter 3
Adjustment
©
National Instruments Corporation
3-21
11. For
x
= (1000000, 2000000, … 15000000, 16000000)
a.
Generate a full scale sine wave at frequency
x
by calling the function
ni54xx_GenerateWaveform
. Set the following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
waveType
—
NI54XX_SINE
•
amplitudeInVolts
—
10
•
frequencyInHz
—
x
b.
Measure the outputs and store the result in the
frequencyResponses
array.
12. Call
ni54xx_CalAdjust
for the terminated frequency response.
The
measuredData
should be the array of output amplitudes.
The
actualData
should be NULL. Call the function
ni54xx_CalAdjust
using the following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
measurementMode
—
NI54XX_SET_FREQUENCY_
RESPONSE_TERMINATED
•
actualData
—
NULL
•
measuredData
—
frequencyResponses
Determining the SYNC Duty Cycle Constants
Two calibration constants, D0 and D1, calculate the value written to
the SYNC DAC to set a specified duty cycle on the SYNC output.
To determine the proper values, use an iterative method by setting the
SYNC DAC to the “best-guess” value (based on the results of previous
guesses), then by measuring the resulting duty cycle. In this section, the
word “tolerance” refers to your defined allowable range other than the
signal received. If the duty cycle is within the tolerance of the desired value,
the calibration is complete. If the duty cycle is not within the tolerance,
calculate the next “best-guess” value and repeat the process. Calculate D0
first by converging on a duty cycle of 50%, then calculate D1 by
converging on duty cycles of 25% and 75%.