NI 9237 for measuring strain

[ganeshnus]

Hi,

      I am using Ni 9237 for measuring strain by using a strain guage. I need to to measure strain for 100 seconds. But in Lab view signal express I get data for every 0.62 milliseconds and even I change the sample size and rate , still it measures at every 0.62 milliseconds. I need to get 10 datas persecond for a period of 100 secs. How can I change the rate and sample size? I tried with continous samples and N samples also. And I varied sample size and rate also, but can't change the frequency of data aquisition. 

Karthik

[KateB]

Set acquisition mode to 1 sample (on demand) with 100ms sample period.
Then, set record option to stop after 10 seconds.

[ganeshnus]

Hi,

              Thanks for your reply and I have done like what you said. But I got the following error and I have attached in this post.I run once only. But it shows DAQ assistant error. Kindly help me. 

Regards,

Karthik

[KateB]

I think 9237 doesn't support 1 sample on demand.

Therefore, you must sampling in continuous mode and set sample to read to 10% of sampling rate.

This equals to .1s sample interval.

Then, change its data into array and collect the first sample of every data chunk.

However, this cannot be achieved with SignalExpress.

Therefore, I'd recommend you to try it with LabVIEW.

I also attached LabVIEW example for your reference.

[vernyew.lim]

Hi Kate and Karthik,

I have spoken with Karthik on the phone and we managed to resolve this issue using SignalExpress. I'm just updating here for reference in case anyone in the future happens across the same issue.

As Kate mentioned, the NI-9237 does not support 1 sample on demand timing. It also does not support low sampling rates like 10 Hz as desired according to Karthik. Therefore in SignalExpress you would have to sample at an accepted sampling rate (here is a list of possible sampling rates: http://digital.ni.com/public.nsf/allkb/593CC07F76B1405A862570DE005F6836) and then use the Subset and Resample step in SignalExpress to resample the signal to the desired sampling rate. It is a workaround as the resultant signal is interpolated from the "real" measured signal but it gets the job done if you must have signals at that sampling rate/interval.

Attached is an example SignalExpress project that could act as an example.

Hope this helps!

[vernyew.lim]

Whoops, forgot attachment.

[ganeshnus]

Hi,

     Thanks Kate and Vern. lab view signal express works with subset and resampling and I try with lab view also.

Karthik 

[Raneiit]

Hi,

vernyew

I am having the same problem with sampling rate but i am unable to open your attachment. I am using signal view express 3.0. So could you please help me