Semi-Period Measurement with 3 synchronously starting Counters

[PCL_805]

Hello Everybody,

I am a very Beginner to the NI DAQ Cards.

I use X Series Cards and want to programm it in C.

My Problem:

I need to measure the Changes of three Digital Pulse Signals over Time , very important is the Phase Shift of the three Pulse Signals to each other.

For that Reason I use 3 Counters connected with the 100 MHz internal Clock as Clock Source.

The three Gates are connected with three PFI Inputs.

I configure the three Counters for Implicit Buffered Semi Period Measurement.

That is, the Measurement starts with Arming the Counters.

The First Starting Egde of the three Counters is set depending on the current ( when Arming ) Level of the respective Signals to measure the Duration between Arming and the next Edge.

After the Measurement has finished, the three Signals are processed considering the Phase of the Signals to each other.

Now my Question:  How can I let start the three Counters simultaneously ?

Is it possible to enable / disable the Clock Source of the three Counters simultaneously ?

Could I use another Counter, which outputs a 20 MHz or 100 MHz Clock as Clock Source for the three Counters ?

Extending the Number of Signals to 5 will require to use 2 DAQ Cards.

Can the Counterstart be synchronized via RTSI Bus in this Case ?

Is there any C Code Example how to implement Synchronization of the Counterstart ?

Many Thanks for Your Help !

Kind Regards

[Alexander_Sobolev]

See here, similar problem

http://forums.ni.com/t5/Counter-Timer/How-to-synchronize-2-Counter-tasks-in-Net/td-p/3221941

In short you need common signal that definitely arrives after all tasks have started. I would disconnect / control Arm or Start trigger, not clock. 

Will PCIe-6612 work? It has 8 counters, no need to use clock over RTSI, and it is X Series NI-STC3.

I would not send signal above 20MHz over RTSI even if they allow to... PXI star trigger allows that, not RTSI.

Clock can be generated with a separate counter, but it will reduce maximum rate from 100 MHz (and hence your resolution) because of minimum pulse low time (4 ticks as far as I remember).