How to acquire both Analog Inputs and Digital Triggers using a NI-USB 6210

[Flonares]

Hi,

I am currently trying to acquire data on four analog channels. This data needs to be indexed by frequency - which I do later, using the initial conditions of the experiment and the scan velocity. I designed my VI to be able to collect data either when the laser starts via software, or using a trigger generated by the laser when it starts emmiting (the code can be switched between the two modes).

For debugging and also to better understand DAQmx, I was wondering how I can collect both analog and digital trigger data, so that I can display them temporally - essentially, I would like to see the TTL signal for the start and the end of the measurement, along with the data. Sometimes, I get data acquisitions which are 0.6s longer than expected, and I would like to understand if this data still falls within the measurement range or if it is obtained after irradiation. I tried to acquire the trigger using a waveform - a bit stupid, I understanding, since we are talking about Booleans - but it felt the best way to record the signal temporally. In the meantime, I removed it from the present VI, as it was broken and the code wouldn´t work properly with it. There are other types of TTL signals that the laser has, which I would also like to capture, but I am a bit clueless on how to properly do it and relate it to the analog inputs obtained.

Any idea on how to implement this idea would be greatly appreciated. 

[ZYOng · Accepted solution]

Use Correlated Digital IO with an M Series Device. Then your DI will be synchronized to your AI data. You can plot both analog and digital data on a Mixed Signal Graph

[Flonares]

Thanks for your kind reply, ZYOng.

That seems to do the trick!

[Flonares]

Hello,

This is a follow-up question on an issue I am trying to solve. I am trying to build a VI that allows me to capture both an analog and digital waveforms. I have now faced a new issue related to the Sample Clock (DAQmx). I´ve read across the board, and found some ideas like sharing the same clock. However, since the clocks are linked to their respective tasks, it seems impossible to share the same Sample Clock across two different tasks (I tried it, and got broken wires. And somehow, I feel it makes sense).

Unfortunately, I feel stuck, as the error message feels a bit cryptic (Is it conflicting with the other Sample Clock?), and I am unable to fix this, so any help would be greatly appreciated. Please find the VI file attached. I am currently using LabView 2023 Q3.

Many thanks in advance!

[GerdW]

Hi Flonares,

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@Flonares wrote:

Unfortunately, I feel stuck, as the error message feels a bit cryptic

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What's cryptic in the message? You request for "SampleClock" and the possible value is given as "On Demand"…

You cannot configure a sample clock for the DAQmx task!

I guess you want to read/write some DIO pins in your task?

The NI6210 only supports "static DIO":

Read the datasheet/specs!

P.S.: It really would help to keep relevant information/questions in one (1) thread, and to keep the correct device name in your message title ("NI6210")…

[Flonares]

Hello GerdW, and many thanks for your reply.

Apologies on my lack of knowledge, this is a field that is far removed from what I do and I am still catching up with the terminology and theory behind it. As such, I have to make a "dumb" question - what does "Static Digital Input/Output" actually means? If I understood correctly from what I have read after googling, it just states that once a value is set, it remains the same until it is changed. If that is correct, how difficult is it to just to get the time stamp for the value switch?

My only goal with this digital acquisition loop was to get the time stamps for when the TTL signal goes HI and when it goes LO - I just want to make sure that the acquisition time interval in the analog channels matches the one set by the triggers. There are other digital channels that I would like to add, since they provide further information on when a certain wavelength is reached, which is important to calibrate the analog data. How can I achieve this?

Trust me when I say that I do my best to read the specifications and research what they mean when I have doubts, but many times I don´t fully grasp their meaning - and that is just part of the learning process, I guess. 

And finally, I will try to group this questions better - some forums prefer these questions to be asked independently, in order to make it easier to find specific solutions to specific issues, and that was the spirit I adopted in my questions.

[GerdW]

Hi Flonares,

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@Flonares wrote:

I have to make a "dumb" question - what does "Static Digital Input/Output" actually means?

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"Static DIO" means: you can set/read "On Demand", but they don't support any sample clock…

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@Flonares wrote:

My only goal with this digital acquisition loop was to get the time stamps for when the TTL signal goes HI and when it goes LO - I just want to make sure that the acquisition time interval in the analog channels matches the one set by the triggers. There are other digital channels that I would like to add, since they provide further information on when a certain wavelength is reached, which is important to calibrate the analog data. How can I achieve this?

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Read the DI channels on demand and use the computer clock for the time information!

You will get jitter in the reading and inaccuracies of the time information in comparison to the time information of the AI channels…

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@Flonares wrote:

And finally, I will try to group this questions better - some forums prefer these questions to be asked independently, in order to make it easier to find specific solutions to specific issues, and that was the spirit I adopted in my questions.

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In this case we would have lost the information on the correct naming of your hardware (because of your typo in the message header) and we would have lost the information on what you want to do…

Generic answer to this thread:

You should gather requirements in the FIRST step and choose your DAQ hardware according to those requirements.

Right now you try to fulfill requirements with some existing DAQ hardware, that doesn't support them…

Buy better DAQ hardware (one-time investment costs) and you don't need to invest so much time (ongoing costs) in developing workaround code!

[ZYOng]

It was my mistake that I thought all M Series DAQ support correlated DIO. Apparently USB-621x are excluded, unfortunately.

Correlated DIO with NI USB M Series DAQ Device