How I can automatically do offset nulling of DAQMX TASK , DAQMX EXPRESS VI

[Ahmed.Arsalan]

Hello Respected Members
I am using 4 strain transducers attached to NI9237 C series module. I have made a State Machine that when so ever i click a button , it executes the DAQMX task(EXPRESS VI) and many Integration and Mathematical operations from the signals generated. I use Gate and Trigger Express VI to get the required amount of signals and when the data is acquired, it automatically goes to the "Wait State". 
Problem Statement: As the transducers face multiple impacts, I want Before every Impact, it should automatically null its offset.( For every impact i click the button,and it enters the state where the DAQMX EXPRESS VI Runs.....). 
Guidance Required on : How to NULL OFFSET , everytime the DAQMX TASK Express VI begins, automatically(without using the interface when we double click the icon of express vi).

Below is the snippet of the DAQMX task stated. Four Different sensors are read by this single task.

[GerdW]

Hi Ahmed,

How to NULL OFFSET , everytime the DAQMX TASK Express VI begins

Two steps:

1. Get rid of the DAQAssistent and use plain DAQmx functions as explained here and in all the example VIs coming with LabVIEW.

2. Do a reading of your channels when starting your measurement and use this reading as "OFFSET" for the next readings. You simply need to subtract that OFFSET from your other readings…

I have made a State Machine

That's fine!

Just add a state of "read offset" between "initialize DAQmx" and "do strain readings"…

[Ahmed.Arsalan]

Two steps:

1. Get rid of the DAQAssistent and use plain DAQmx functions as explained here and in all the example VIs coming with LabVIEW. Done! Using NIMAX Configured Task. 
Now i get 200279 error, i have also tried removing the big while loop and creating a small while loop around the Read VI..... Not Helping at all... Not going anywhere yet.

[GerdW · Accepted solution]

Hi Ahmed,

have you tried to run an example VI on its own? (Like voltage, continuous acquisition)

They are great to learn the usage of all those DAQmx functions and to understan, how they interact…

On your image:

- you should set the sample rate only once before the loop

- you should start the task only once before the loop

- you need to read the DAQmx data without an additional wait (or very slow computation) in the loop

- the error message says "you have been to slow with read the next block of data"! (You surely got the error -200279, don't you?)

Simple example of steps to take:

[Ahmed.Arsalan]

Thanks GerdW.
Now can you guide me using of the null offset vi of all the 4 strain tasks.

I am attaching a snippet of present situation. 

Thanks Alot for your kind help

Regards

Ahmed

[Ahmed.Arsalan]

Sorry for the bad snipp

the correct snipp

[GerdW]

Hi Ahmed,

Now can you guide me using of the null offset vi of all the 4 strain tasks.

I already guided you with this snippet above.

How should I help you with your images? Should I use Paint to draw in them? Why don't you attach your VI?

Btw. there's just one task in the image, not 4 of them…

[Ahmed.Arsalan]

Respected Sir, 

I am talking about the DAQMx Perform Bridge Offset Nulling Calibration.vi. It requires the input of channels. Kindly guide me about the channels please. I want to use this vi, as i can have values in negative as well. Minus Minus add and the error is doubled now.... 
About the Task, Yes its a single task configured in NIMAX having 4 sensors. attaching a pic.

About the VI, Sure i can send you the complete 2MB VI. But it will take alot of time to understand it sir, I am a Civil Engineer and made this VI with the Very Very Basic Knowledge of LV. Thats why perhaps i m troubling a KNIGHT
Thanks alot GerdW. 

[GerdW]

Hi Ahmed,

I am talking about the DAQMx Perform Bridge Offset Nulling Calibration.vi. It requires the input of channels

It only requires to name the channels when there are channels in the task which are NOT bridge-type sensors! By default all channels in the task get "offset calibrated".

Did you read the help for this function?

Sure i can send you the complete 2MB VI.

You may use ZIP to compress the file for upload…

[Ahmed.Arsalan]

Thanks alot sir. I have read the manual of vi now. Previously i had more focused on the connection descriptions... my bad. apologies.

presently i am on mobile, i will surely send you the vi.

regards

Ahmed