Multifunction DAQ

cancel
Showing results for 
Search instead for 
Did you mean: 

trigger not responding & extremely noisy acquisition

I have constructed a
- N channel
- N Samples
- Analog Triggered
Data Acqusition system. The program was working fine except that the singals were unsually noisy.
So I replaced a regular ribbon cable with a shielded one. However when doing this I did not turn off the computer.
Now the board does not trigger with the regular trigger pin(TRIG1). I checked the impedence of the pin and found that it was really low.
Does this mean that the pin is damaged?
I tried to use TRIG2 but it works sometimes and not at other times.
The other analog input channels seem to be working fine.
The unusual amount of noise also remains. (Which cause the acquisition to trigger even when there is no signal and hence is very an
noying)
Thanks.


NI Software : LabVIEW version 7.0
NI Hardware : Multifunction DAQ device PCI-6023E
Driver Version : MAX 2.0
OS : Windows 2000
0 Kudos
Message 1 of 4
(2,245 Views)
Hello,

Thank you for contacting National Instruments.

PFI0/TRIG1 and PFI1/TRIG2 should operate in the same fashion. You should be able to implement a digital trigger using either connection. A digital trigger will fire when an edge is detected on a particular pin. You can configure a rising or falling edge trigger. The trigger input accepts a TTL level signal which means if you have a rising edge trigger configured, the trigger will fire once the voltage changes from 0V to at least 2V. If this transition occurs the trigger will fire. Therefore, if you have noise spikes on your trigger signal that are large enough to trigger your acquisition, you will need to add some type of filter to remove the high frequencies of the noise. This can usually be acc
omplished with a simple single-pole RC filter.

If you feel confident that your PFI0/TRIG1 pin is damaged, you can return your board to be repaired. However, in most cases you should be able to get by using either PFI1/TRIG2 or one of the other six PFI lines.

Regards,
Bill B
Applications Engineer
National Instruments
Message 2 of 4
(2,245 Views)
Hi,
Thanks. The TRIG1 pins worked fine (and there was less noise) once I removed the 50 Ohm terminators I had put on unsed signals. But this raises another question - Do I need to terminate the unused digital channels as they may act like antennae and add to noise.
0 Kudos
Message 3 of 4
(2,245 Views)
You do not need to terminate the unused digital channels. However, if it makes you feel more comfortable, feel free to terminate them.
0 Kudos
Message 4 of 4
(2,245 Views)