Chapter 3
Adjustment
©
National Instruments Corporation
3-11
5.
Enable the analog filter by calling the function
ni54xx_SetAnalogFilter
. Set the following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
filterState
—
NI5XX_ENABLE
6.
Measure the outputs (
amplitudeWithAnalogFilterEnabled
).
7.
Feed the measurements from Steps 4 and 6 to
ni54xx_CalAdjust
. The
measuredData
is a pointer to the value of the output with the filter
enabled, and the
actualData
is a pointer to the value of the output with
the filter disabled. Call the function
ni54xx_CalAdjust
using the
following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
measurementMode
—
NI54XX_SET_A7
•
actualData
—
&lowFrequencyAmplitude
•
measuredData
—
&litudeWithAnalogFilterEnabled
Determining the Low Frequency Gain of the Pre-Amplification
10db Attenuator (Constant A8)
To determine the value of constant A8, generate a low frequency sine
wave output with the attenuator disabled and measure the outputs. Repeat the
process with the attenuator enabled, and pass both results
to
ni54xx_CalAdjust
. You can measure the amplitude, peak-to-peak
amplitude, or RMS value, as long as both measurements are the same.
1.
Set the offset calibration DAC to 0 by calling the function
ni54xx_SetOffsetDAC
. Set the following parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
DACValue
—
0
2.
Set the gain calibration DAC to –4079 (the approximate value for a gain
of 1) by calling the function
ni54xx_SetGainDAC
. Set the following
parameters:
•
sessionHandle
—The handle of the calibration session for the
device
•
DACValue
— –
4079