genera-quarter bridge strain measurement using cDAQ

[lopez]

Can't find a group for compact DAQ so hope this is in line,

I have a couple general questions about seting up a quarter bridge strain guage using the Compact DAQ.

I am using an NI 9445 bridge completion accessory, which is appropriate to use as a configuration, quarter bridge completion I or II.? I think I but not sure. I do not plan on attaching any extra resistors.

How can I copy the setting from one module to a second module?

thank you

[TheWoost]

Hi lopez,

I believe the bridge completion accessory you are referring to is the NI 9945, and I assume that you are using it with the NI 9237 4-Channel Bridge Module.  The appropriate configuration depends on the actual strain gauges you are using and the kind of measurement you are trying to obtain.  There is a detailed document in our Developer Zone with information about the different Strain Gauge configuration types that can be found here.

To address your question about copying settings from one module to another, are you referring to the NI 9237?  What particular settings are you wanting to copy?

Regards,
Andrew W
National Instruments

[lopez]

TheWoost,

I am using the cDAQ 9237 strain module with 4 inputs and the 9945 completion accessory.  I am using a single strain guage with two leads.  I don't understand the quarter bridge completion 1 vs 2 setting on MAX setup page for the strain guage.  I only have one possible wiring option according to the 9945 wiring diagram.

I need to use two 9237 modules as I am acquiring 7 signals from single strain guages (quarter bridge).  I would like to copy all the strain guage setting as it is rather tedious to input the setting for each strain guage (I will need to switch them depending on measurement).  this includes such things as guage factor, max and min, quarter bridge.  All the settings assigned in MAX.

Thank you

[TheWoost]

Hi lopez,

It sounds like the strain gauge that you are using is probably a Quarter-Bridge Type I since your transducer doesn't seem to have a temperature-sensing element.

I would recommend setting up a single strain gauge measurement task in MAX that includes all 7 channels for your strain gauges.  However, there is no way to copy the contents of the settings from 1 strain gauge into another.

If all 7 of the strain gauges' settings need to be changed at the same time, you could just create a second task that includes all of those settings and use it as necessary.

Regards,
Andrew

[KyleBryson]

Hi lopez,

When you are editing a task in MAX, you can shift-select all of the channels that you would like to change (click on the first channel in the list, hold shift, and click the last channel in the list).  As long as they are all selected, any changes you make to the configuration on the right will apply to all of those channels.  It's not quite copying, but it might work for what you need to do.  I'm attaching a picture where I changed seven channels of a strain task to the quarter bridge configuration.

Hope that helps.  You could programmatically create the task and assign properties to all of the channels in LabVIEW or your development environment as well, if you expect to be using many different configurations on different systems.  Saving a couple of tasks in MAX is probably easier to just set up most applications.

Kyle

[lopez]

TheWoost and KyleBryson,

thank you for the tips, very usefull