Misread voltages in task (7.35V max reading on 10 V signal)

[Linkster]

Hello,

I have  a USB 6212 DAQ board with Labview 7.1.  I have two load cells connected to amplifiers with 0-10V output and an encoder that I'm trying to sample.

When I pull a single measurement using "DAQ MX read 1 channel 1 sample DBL", I get the full scale value of whatever the reading is from that amplifier.(0-10V)  But when I try to sample between 30-130 Hz my voltages have a max value of 6.25V even if they exceed that value.

I have attached the sequence that starts the timer and the encoder task(DAQ updater) and the one that configures the analog task(Sampling), and the one that takes and scales the voltage measurements from the analog task(Read anlalog inputs array).

I'm not looking at my scaled values either so I don't think that's the problem.  When I was troubleshooting this I was looking at the raw voltage data array that the "DAQ MX read N channel N samples" outputs.

Any ideas?

[RT4CY]

Hi Linkster,

I would start by ensuring that the hardware is working properly.  A great hardware troubleshooting tool is Measurement & Automation Explorer (MAX).  You can find this program by going to Start»All Programs»National Instruments»Measurement & Automation.  Locate your device under NI-DAQmx Devices.  Right-click on your device and create a Custom Voltage with Excitation task.  Make sure to configure the task using the proper channel, excitation value, etc.  You can choose your sampling mode (1 sample on demand, continous at a specified rate, etc.) in the task as well.  By clicking Run, you can acquire data and display it on the graph above.  Make sure you have the most recent version of DAQmx before doing this.  See the attached images for a step-by-step on creating the task in MAX.

[Linkster]

Rod,

Thanks for the advice.  I think I figured out the problem.  When I configured the task for the two voltages, I hadn't wired the max or min values for the task.  The defaults were set to -5 to 5 and I need 0 to 10.

Thanks again.

Linkster