Why is the the BNC Analog output of USB 6221 clipped when it exceeded 1V range

[munhu]

I am new to both labview and DAQmx. I generated an analog output sinusoidal signal using LabviewSignalExpress and the Ni-USB 6221 hardware.  All seems fine when I check the signals on LabviewSignalExpress display, for an output range of -10V to +10V which happens to be the default. I then connected the BNC AO 0 (analog output 0) to a Tektronix oscilloscope to view the generated signal. It tends out that if the range exceeds 1V, the output gets clipped. What could be the reason? Any idea would be greatly appreciated.

[j.terao]

Hi, Munhu

There are a couple of things that you can try to check.
1. Check if the amplitude of the signal is set to 1.00
If it’s set to 1.00, how much does it exceed from 1/-1 scale?
2. If you change the amplitude of the signal from Ao0 (i.e 2V, 500mV), does it still exceed the range?
3. Try using LabVIEWsample VI to see if there is still the same behavior.
Open LabVIEW>help>find examples> hardware input and output>DAQmx>Voltage >Cont Gen Voltage Wfm-Int Clk.vi

National Instruments,Japan

Applications Engineer

Junichi

[munhu]

Junichi-san- Thank you for your reply. If I change the amplitude to a value greater than 1V, for example 2V the output always gets cliiped at 1V. Any value below 1V does not give a clipped output.This is when I output the signal to an oscilloscope. However if I check the output signal on Data View Displays in Signal Express gui no signal appears clipped. I also tried to loook for the vi you refered to in 'LabVIEW>help>find examples> hardware input and output>DAQmx>Voltage >Cont Gen Voltage Wfm-Int Clk.vi'. The 'Hardware input and output' folder that I have does not have the DAQmx folder. I have labview2010 installed on XP. 

[j.terao]

Hi Munhu

When you say “gets clipped”, do you mean a signal you are outputting is out of the oscilloscope’s display?  When you outputted the signal of 2V, what was the range in oscilloscope’s display?

If you set the range in oscilloscope (i.e +/-5), and output 2V, does it still “get clipped”?
Please make sure that the range in oscilloscope is higher than the signal.

Since you are seeing a right signal in Signal Express (that means your device outputs right signal), it sounds like your problem is something you should deal with the oscilloscope.

Regarding no 'Hardware input and output' folder, did you install NI-DAQmx after you installed LabVIEW 2010? NI-DAQmx is a driver to do Data Acquisition with our hardware.
If NI-DAQmx was installed before LabVIEW2010, NI-DAQmx cannot be applied to LabVIEW 2010, therefore you should always install drives after installing LabVIEW.

Junichi