Function Generator to check phase sync between two AI channels

[StathPol]

Is there any way to connect a function generator or with an oscilloscope with a NI module to see whether the sinewave graphs of two analog input channels are not loosing phase for sync purposes? For this LabVIEW 2014 will be used to generate the code. 

Thanks. 

Pepis21

[CBond]

Hi Pepis21,

I would like to help you on this, but first I would like a bit more information about your application. Which NI module are you using, and which oscilloscope and function generator are you looking to use? What is this application for, and any other details about your specific application might be useful to know.

Thank you,

Cody

[StathPol]

Hi Cody,

I am using the NI 4330/4331 module for strain and load measurements. The function generator (TG1304) and oscilloscope (TDS2014) are attached in the images below.

The application is for a dynamic test including sync of 16 AI channels. For the NI 4330/4331 module, 8 modules will be used. The goal is to verify that the sync of the sensors is achieved avoiding any signal path (loosing phase), individual board timing and jitter. For this purpose, I have written a code in LabVIEW for possible sync.

I am wondering whether there is any possibility to connect the function generator with an oscilloscope and then with the NI 4330/4331 module (without the sensors attached) to see the graph of the two channels for example and check the LabVIEW code. I intend to use an optical switch as a trigger to check whether the two AI channels start at the same time.

Please let me know whether further information is needed for clear explanation.

Regards,

Pepis21

[CBond]

Hi Pepis21,

I understand that you are worried about the sensors losing phase, but DAQmx is very powerful, so if you are using one task for the testing of all 16 channels, then they will already be in sync and there is no need to test this. 

I hope this helps and saves you time on your project!

Thank you,

Cody

[StathPol]

Hi Cody,

Thanks for your suggestion. Indeed, DAQmx is a powerful tool to handle things. Can we actually use 16 AI channels from 2 different modules 4330 and 6361 in one task including strain and voltage outpouts? We need to somehow verify that the sensors are not out of phase, and if they are what is the cause of it. That is what I really want to find out for verification purposes. 

Regards,

Pepis21

[CBond]

Hi Pepis21,

You can use 16 AI channels from the two different modules as long as they are simultaneously sampling. This is fine for the 4330, but the 6361 is not simultaneous and so all channels on the 6361 besides the first channel will be out of phase by an amount determined by the convert clock. This will be the only phase difference, so you do not need to determine the cause by other means.

There are similar devices such as the 6356 http://sine.ni.com/nips/cds/view/p/lang/en/nid/209075 which may be of interest to you.

[StathPol]

Hi CBond, 

Thanks a lot for your reply. I would like to clarify something related with your answer. You are suggesting to use all channels in one task. This is absolutely fine but the main problem is that we do have bridge and voltage modules. Please take into account that strain gauges and load cells include bridge and scaling information. What do you think for one alternative by creating two tasks; 8 channels for 4330 and 8 channels for 6361. My main concern is to split the 4 strain gauge and 4 load graphs in an alalog, multiple channels 1D graph.

[CBond]

Hi, 

These problems should not be an issue in using all channels in one task, which would be your best option for synchronisation. My colleague Vivien, who I know you have been in contact with, is working on your code and will get back to you next week. 

[Henrik_Volkers]

Depending on your input level for the channels. it's quickly done to wire all chnnaels to one signal generator source (all with identical length, 1m cable is about 4.5ns delay). Set the Generator to sine of the highest frequence of interest. capture 20+x periodes, use tone detection to measure the phase.