National Instruments Welding System 321645c-01 Manual De Usuario

Chapter 2

Function Reference — AO_Change_Parameter

©

 National Instruments Corporation

2-35

NI-DAQ FRM for PC Compatibles

On some of the devices, you can phase-lock the internal timebase to an external reference 
clock. The internal timebase can be an integral multiple of the external reference clock. This 
feature is useful because you can synchronize the timebases of multiple devices so that they 
are all locked to each other.

On DAQArb 5411 devices, you can phase-lock the internal timebase to a non-National 
Instruments device using the I/O connector or to a National Instruments device using the RTSI 
connector. You can select the reference clock source by using the 

Select_Signal

 function 

call. If the PLL reference clock source is the RTSI clock, set the reference clock frequency to 
20 MHz.

To change the PLL reference frequency, set paramID to 

ND_PLL_REF_FREQ

.

The SYNC output is a TTL version of the sine waveform being generated at the output. It is 
obtained by using a zero-crossing detector on the sine output. It is generated on a separate 
output connector instead of the main analog output connector. The SYNC output might not 
carry any meaning for any other types of waveforms being generated.

You can vary the duty cycle of TTL output on the fly. To change the SYNC duty cycle as 
the percentage of the time high, set paramID to 

ND_SYNC_DUTY_CYCLE_HIGH

.

The 

paramValue parameters imply percentage (%). To disable the SYNC output, set the 

Table 2-13.  Parameter Setting Information for the Trigger Mode

DAQArb AT-5411 
DAQArb PCI-5411

Yes

ND_SINGLE 

ND_CONTINUOUS

ND_BURST 

ND_STEPPED

ND_CONTINUOUS

Table 2-14.  Parameter Setting Information for PLL Reference Frequency

DAQArb AT-5411 
DAQArb PCI-5411

Yes

1,000,000, 

10,000,000, 

20,000,000

1,000,000