strain measurements using SCXi 1314

[sfjd]

Hi,
How to configure in MAX the SCXI 1314(PXI 1052 and 1520) to take load cell measurement? I tried to create a task usin analog input ->strain, but it does not work. It is showing some flucturaing signal when I click the test icon. I am using a load cell of 2 gauge factor and resistance 120 ohms. Can anybody help? It is a full bridge connection.

[devchander]

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How to configure in MAX the SCXI 1314(PXI 1052 and 1520) to take load cell measurement?

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Are you using LabVIEW??

If yes, to start with DAQ express vi, also take a look at relevant examples shipped with LabVIEW

[sfjd]

I am using measurement and automation to create a new task of loa cell measurement. I have tried with creating a new task with Analog voltage measurement and analog strain measurement. I am getting some erroneous signals which is drifting. Also when I tried to calibrate it is giving error 200380.

[Jarrod_B.]

Hello sfjd,

Please refer to the Knowledge Base Error -200380 When Calibrating SCXI-1520 in NI-DAQmx which addresses the error you are getting.  Double check all of your task settings to make sure that they are correct.  Let us know if you are still having trouble after following the advice in this KB. 

Best regards,

Message Edited by Jarrod B. on 11-27-2006 12:02 PM

[sfjd]

Hi,

I am using only the null offset only so the shunt calibration is out of question as requested by you. Even with only one load cell I am not able to take the reading. Please help immediately. I am waiting for the past one week to sort it out. I have gone thorugh the document for 200380 before posting it online. Please give some step by step suggestions or what may cause the problem? A step by step (simple enough to understand) procedure to take readings. I have done the following steps:

1. Create a analog voltage measurement task in the Measurement explorer.

2. Input the range of measurement (I am using a 200 kg loadcell). the input was -200 to 200.

3. Scaled it using map range to -0.002 to 0.002.

4. Click Test.

5. Some drifting fluctuating signal

6. I added some weights (known - 10kg) over the load cell.

7. Click Test.

8. No change in the output.

In between I tried with analog strain task also. No good result. I tried calibration from the tab inside thes strain task. error 200 380.

If there a way to sort it out. We are not able to use the DAQ because of this problem....

Please give a help as fast as you can..

Thanks

1

[Jarrod_B.]

Hello sfjd,

Instead of using an regular voltage input task or a strain task, try using the Custom Voltage with Excitation task as described in How do I Configure a Load Cell in MAX?.  Again, make sure that you specify your input limits in terms of the scaled units of any custom scale you apply.  More information about setup and testing in MAX can be found on pages 3-8 and 3-12 in the SCXI-1520 User Manual.

Finally, make sure that when you are peforming the null offset compensation, you have no load applied to your load cell.  As pointed out in the previous KB I mentioned, there is only a finite voltage range that the module can null. 

Please try these steps and let us know if you are still having trouble.

Best regards,

[sfjd]

Hi,

Please note the following.

I have followed your instructions and created a custome voltage task using MAX. I entered max as 200 and moin as -200 and using map range I entered the following data:

prescaled: max: 0.002 and min -0.002

Scaled: max: 200 kgs and -200 kgs

Full bridge and 2mV/V connection.

In the settings tab I entered max as 200 and min as -200.

When I click "test" I am getting an ever increasing fluctuating signal. Do I need to do anything else to take measurements using the load cell? Please give step by step instructions without redirecting to some othe links which in my case is not working.

[sfjd]

Hi,

Please see the attachment.

[Jarrod_B.]

Hello sfjd,

It sounds like you are configuring the task correctly.  Based on the description you've provided, it sounds like the signal you are measuring is floating.  Perhaps there is something wrong in the physical connections.  Please double-check your wiring with the appropriate diagram in Chapter 2 of the SCXI-1520 User Manual.  There is a separate diagram for each type of bridge configuration.  (These references to external documentation are here for the benefit of everyone reading this thread). 

Please list the connections you've made so that we can verify proper wiring.  Once we've confirmed that your connections are good, we can look for other potential problems.  The next troubleshooting steps would be to try connecting different strain gauges (to rule out a problem with the sensor) and to try taking readings on different physical channels of your 1520 module (to rule out a hardware problem with a particular channel). 

Best regards,

[sfjd]

Dear Jarrod,
We purchased three nos of 1314 and one 1315. I have tried to connect to the other 1314's but with no useful results. I also tried to connect with other load cells also. I checked the loadcell using a digital multimeter which shows correct results with known weights. Any further clue? I have connected the wires to P+ and P- as well as S+ and S-. At present I have connected only one load cell. As I mentioned earlier it is a full bridge conncection.

Message Edited by sfjd on 12-11-2006 10:48 AM

Message Edited by sfjd on 12-11-2006 10:49 AM