Connect DAQ AI and Counter input to the same input signal

[-Raul-]

Hello,

In our application we need to analyse some PWM signals. We need the PXI-6229 DAQ to determine the following:

- Pulse Width.
- Period.
- Separation between two falling edges (of two independent signals).
- Amplitude of the pulse (Voltage peak-to-peak).

My question is: can we connect those signals to AI of the DAQ (for measuring the amplitude) and simultaneously to the counters (digital inputs) for measuring the other parameters? Please see attached an schematic displaying the routing of the signals planned.

Thank you.

[Marshall_B]

Hi Raul,

Is there a particular reason why would want to input a PWM signal to the analogue input channels of the device rather than the digital inputs? 

You should be fine doing this with the PXI-6229 as it has 32 analogue inputs and 2 counters, each with 32-bit resolution.  As long as you wire the signal source to each of the respective channels on the PXI-6229 there should be no problem.

Let me know whether this helps.

.

[-Raul-]

Hi Marshall,

Thank you for your reply. We need to analyse the amplitude peak to peak of the pulses for each PWM signal, so we need the DAQ's Analogue Inputs to give us that value, right? Can the counters also provide the amplitude of the signals being sampled, in addition to the timing parameters?

Thank you,

Raul

[Marshall_B]

Hi Raul,

Yes, that is correct.  However, whether you will be able to to do this with the PXI-6229 hardware depends on the signal you are trying to acquire.  You will not be able to obtain amplitude readings from the counters as counters only look for certain events to occur and not amplitudes.

I understand that my colleague is currently helping you via SSP phone support and that you have gone considerably further into discussing the problem with them.  If it is OK with you, I think it would be best that I allow my colleague to help you from here on so that you do not have to unnecessarily repeat any information.

Thanks

[Chris-NI]

For the sake of completion so that others on the forums may find this thread more useful, I think it is helpful to add that the impedances on the 6229's analog and digital lines are such that you should be able to simultaneously connect your signal to both an analog input and a counter input (in parallel) without significantly degrading your signal (some current leakage will occur on the digital lines).  This is of course all relative and may have a larger impact if your external system has a higher impedance with respect to the 6229.  Take a look at the specifications for the 6229 for the exact impedance on the inputs for more information, here:

NI 622x Specifications - http://www.ni.com/pdf/manuals/371290g.pdf

Regards,