Detect TTL signal using configured acquisition

[Paritosh]

I am using configuired acquisition to acquire signal in NI PCI 5105 in visual studio 2008. The other signals are fine but when I give a TTL signal input having a low duty cycle, it can not detect the TTL signal. Is it because it has low duty cycle? The signals that are coming only shows the value around 0. I tried to connect the same signal to NI Scope front panel and it is showing the correct signal. What can I do to solve this problem? I've attached a screen capture of scope front panel. Here we can see the trigger signal in channel 1 but this signal can not be seen using configured acquision.cs. Please help..

[Rohama_K]

Hi,

How low is your duty cylce? Is configured acquisition.cs example code or something you have written? Are you able to trigger if you increase your duty cycle?

[Paritosh]

The duty cycle is as low as 0.4% I have used configured acquisition.cs that NI has provided and made some changes in it. I even tried with the unchanged code but it is not showing the TTL signal. I used the 1 KHz sinusoidal signal in the same channel and its working fine. Please help me with this.

[Travis_Ann_N]

Hi Paritosh,

It seems your duty cycle is very low. The duty cycle tolerance for the PCI-5105 is 45% to 55%. Specifications on the duty cycle are listed on page 11 of the PCI-5105 Manual. Does that help to answer your question?

Regards,

Travis Ann

[Paritosh]

But I am getting the signal in Scope Soft Front panel as you can see in the attachement in my previous post. Also, I used the same TTL signal as a trigger in a labview program. I need this signal in channel 1 to act as a trigger for channel 0 source.

[Travis_Ann_N]

Hi Paritosh,

Can you clarify for me how you have you triggering configured? I see that in your SCOPE Soft Front Panel shows that you are using rising edge trigger CH 0 (sine wave) to trigger CH 1 (TTL), but you describe that your code is trying to trigger off of CH 1 (TTL) to trigger CH 0 (sine wave). 

Also, what is the frequency and voltage range of these signals? 

Regards,

Travis Ann

[Paritosh]

The trigger in the attached picture is just to test. The real trigger will be the TTL signal in channel 1. The TTL signal is a rising edge trigger in channel 1. The frequency is maximum of 1 KHz but it sometimes can go down to 200 Hz or 500 Hz as well. The voltage is around 4 volt and the trigger level is around 3.5 V. 

[Travis_Ann_N]

Hi Paritosh,

From what you are describing, it sounds like what you have set up should work. Could you post some screenshots of your set up so we could take a deeper look?

Regards,

Travis Ann

[Paritosh]

Sorry for replying late..Actually I managed to get the TTL signal as a trigger as you can see in the attached image. However, the data acquiring rate is too slow although the data is coming to the digitizer at 1 KHz. I am taking 500 records for each signal.  How can I speed up the acquisition time? Please help me on this..

[Travis_Ann_N]

Hi Paritosh,

The acquiring sample rate is set in the Configure Horizontal Time function in the NiScope driver, so if you want to acquire at a faster rate, you will implement that in your code. You are limited to the overall acquisition rate of the card, which in your case is 60MS/s. 

Regards,

Travis Ann