NI 9401 module counting problem

[lakersrl]

Hello,

I'm having difficulties counting the correct value with from the NI 9401 counter (5th module of the NIcDAQ 9172 board). The value I should be recieving is 30 times higher than what I am actually receiving from the counter. I've attached a Oscilloscope to the counter to measure the pulse signal of counter 0 (14th pinout of module 9401) from a condensation particle counter (CPC). From the oscilloscope I obtain a pulse width of 300 ns, 4V high with a TTL pulse type. I am currently using the Counter Read VI (Counter U32, 1 sample) in a loop.Im using rising edge with counting up direction. The CPC had a flow rate of 1.5 LPM. In a time of 60 seconds, the counter from labview Counter U32 VI read 17000 counts. Theres a timestep of 0.1250 s, such that 91 counts/ cm^3 occur while the CPC read a number on the order of 2700 per cm^3, hence much larger than the incorrect number from the counter. Any help would be greatly appreciated. 

Thanks

[lakersrl]

this would mean that I would need approximately 500,000 counts rather than the 17,000 counts Im receiving from the counter. Any help would be greatly appreciated.

[Brian_P]

lakersrl,

I am sorry that you are not receiving the right number of counts.  I think our first step in diagnosing this issue would be to first remove the software portion of this issue.  Let's eliminate LabVIEW from the equation and first try counting in Measurement and Automation Explorer.  To do this:

1) Under Devices and Interfaces, under your 9172 chassis, right click on your 9401 module and click test panels...

2) Click the Counter I/O tab at the top of the screen.

3) For mode choose edge counting.

4) Select the proper PFI Line and start.

This will let us know if there is a problem with the hardware counting or if there is a problem in software.  Please let me know the results.

Regards,

Brian P.

[lakersrl]

Hello,

Thansk for the help. When I try to do as you stated before I obtain the error: -50103, specified resource is reserved.Where should I go from here?

[Brian_P]

lakersrl,

I am sorry that you are getting this error.  Are you perhaps running your LabVIEW code and Measurement and Automation test panel at the same time?  I also found a Knowledgebase article that has a few scenarios that might throw this error.  I would check this out and make sure that one of these things isn't happening.  This article also contains some helpful fixes for this error.  Please let me know if this helps.

Regards,

Brian P.