How to synchronize NI 9219 and NI 9237 to get 2 voltage readings from NI 9219 and 1 strain gauge from NI 9237 at 10 Hz rate?

[Egemen]

Dear All,

There is a synchronization problem between NI 9219 and NI92373. Altough Rate =10 Hz defined, the collection time rate is: 1612.9 Hz, time step: 0.00062 sec. See the attached text file for a sample data.  This number comes from spec sheet of  NI 9237 page 21. fm=12,8Mhz, fs=12,8Mhaz/256/31=1612.9 Hz. How can we make this vi to get 2 voltages and 1 strain at 10 Hz? How can I synchronize NI 9219 and NI 9237 to get data at 10 Hz?

 A possible solution is cited in specs sheet of NI 9237 at page 20-21, which I could not understand how to do? (all modules sharing a master time base ? How?)

Attached are the vi and the file it creates.

Note: The hardware in my work is : cDAQ9178 chassis, NI 9219 for 2 voltage measurements, NI 9237 for 1 strain gage measurement.

Best wishes,

Thank you,

Ege

[Steven_K.]

Hi Egemen,

The NI-9237 has a minimum sampling rate of 1612.9Hz. What you will need to do is to sample at a common higher sampling rate, like 2000Hz, then decimate the data. There is a decimate VI that will keep every X*n samples where X is some multiple (if you choose to use 2000Hz use 200 for X). Here is a link to it:

LabVIEW 2010 Help: Decimate (continuous) VI

[Egemen]

Dear Steven,

Thank you for your help. I am sending you 2 vis and 2 output files of these 2 vis. The VoltStrn1.vi writes two voltages and 1 strain with 2000 Hz to VoltStrn1_lvm file. In order to Decimate the data from 2000Hz to 10 Hz, Decimate.vi is included in VoltStrn3.vi and the output of VoltStrn3.vi is VoltStrn3_.lvm.

As you see in the VoltStrn3_.lvm , the VoltStrn1_lvm is not Decimated from 2000Hz to 10 Hz. I would be pleased if you can adjust the VoltStrn1.vi so that it will give the same 2 voltages and 1 strain data in an output file at 10 Hz rate.

Thank you ,

Note: The hardware in my work is : cDAQ9178 chassis, NI 9219 for 2 voltage measurements, NI 9237 for 1 strain gage measurement.

Egemen

[Egemen]

Dear Steven,

Please consider this messagei, not previous one.

Thank you for your help. I am sending you 2 vis and 2 output files of these 2 vis. The VoltStrn1.vi writes two voltages and 1 strain with 2000 Hz to VoltStrn1_lvm file. In order to Decimate the data from 2000Hz to 10 Hz, Decimate.vi is included in VoltStrn3.vi and the output of VoltStrn3.vi is VoltStrn3_.lvm.

As you see in the VoltStrn3_.lvm , the VoltStrn1_lvm is not Decimated from 2000Hz to 10 Hz. In VoltStrn3_.lvm, the time column is all zero, and the Comment column gives strain, voltage 1, voltage 2 respectively. If you compare the values in VoltStrn1_lvm and VoltStrn3_lvm, you can see that the 2^nd column of VoltStrn3_lvm is the sequantal data of VoltStrn1_lvm, 2 voltages and 1 strain.

I would be pleased if you can adjust the VoltStrn1.vi so that it will give the same 2 voltages and 1 strain data in an output file at 10 Hz.

Thank you ,

Note: The hardware in my work is : cDAQ9178 chassis, NI 9219 for 2 voltage measurements, NI 9237 for 1 strain gage measurement.

Egemen