measure multiple frequencies with one cdaq9178 and one NI 9401?

[Madmax14]

Hello, 

I am trying to measure two dynamic frequencies with a cDAQ9178-Board and one NI9401-Card. The frequencies arrive as TTL-Signals and are routed to the Inputs PFI0 and PFI4. When i try to monitor the signals in DAQMAX, i can´t separate them. On both lines the Counter registrates the flanks from both signals. If i just connect one Signal to one of the Inlines, i don´t have any interferrence, but if both wires are connected both signals occur on each line. Do you suggest a wiring-Problem or is there in interferrence elsewhere? 

[Corey.Rotunno]

How are you wiring them up? Sounds like maybe you have connected both SRC and GATE? 

Also, to use counters 1&2 you would be using PFI 1 and PFI 4, not PFI 0 and PFI 4.

The link below could solve your problem. It is for a NI9411, but applies to the 9401 as well.

https://forums.ni.com/t5/Counter-Timer/Physical-Connections-to-use-4-counters-with-NI-9411-in-cDAQ-9...

And the link below contains the pinout and PFI assignments chart for the NI9401 about 3/4 of the way down the article.

http://www.ni.com/tutorial/7109/en/

Best of Luck!,

[Madmax14]

Hello Corey,

the first signal is wired to pin 14( PFI 0, CTR 0 SRC) and the second one is wired to pin 20 (PFI 4, CTR 1 SRC).

PFI 1 would be pin 16 (CTR 0 GATE), right?

thank you and best regards 

max

[Corey.Rotunno · Accepted solution]

My mistake, I was wrong. This is the document I used to get up and running. It appears for your card PFI 1 & 5 might be the ticket if you are doing single counter frequency measurements. If you are using the 2 counter measurements then it's a little different.

https://zone.ni.com/reference/en-XX/help/370466AC-01/mxdevconsid/cdaqcountsigconn/

Out of curiosity, where are the ground for your TTL signals tied to? I use the same common as your counters are using.

[Madmax14]

The ground for the TTL-Signals are tied to different meaurement-card(NI 9205). I am using two meausure-hubs for torque and rev measurement. The ground is important as reference for the voltage. should i also connect the ground-lines to the COM-Pin of the NI 9401?

[Corey.Rotunno]

Yep

[Madmax14]

hello corey, 

now with both TTL-ground also wired to the COM-pin of the NI9401, the interference between the signals is gone. Torque and rev-measurement are working properly.

Thank you very much. 

max

[Corey.Rotunno]

Good to hear and thanks for the kudos!