USB 6008 mV data acquisition

[07875193382]

Hi All,

I am using a USB 6008 student kit DAQ card. I am trying to collate the data from my torque transducer which provides me an output of 1.5mV/V for every N-m torque application. Transducer is working fine and have verified it by performing the RR tests on it using a multimeter. The problem arises when I use the DAQ card, and it does not provide me intermediate readings. I am only able to get the full scale readings @100N-m. In all other scenarios, I would not get the expected voltage reading. I am using the same card for another sensor to measure angles, and it is working absolutely fine with that.

I repeat, it is the torque transducer readings which am not able to collate. I do not get the intermediate readings (e.g. 30, 40, 50 N-m). Although  I am able to get the full scale reading of 100 N-m.

I am using DAQmx 8.1 and VI logger 2.1 software which was given to me with the student kit version.  My attempt with manipulating the sampling rate of the data acquisition mode has also gone in vain. I have tried sampling rates as low as 10 samples per second to 2K samples per second (continuous mode). Any suggestions for this problem would be of great help.

Many Thanks,

Manju Sharan

[Chris_Rake]

You may be encountering a change in the measurement due to the input impedance of the 6008.  What happens when you measure the voltage while the sensor is attached to the 6008? 

[07875193382]

Hello Chris,

When I use the inclination sensor, I get accurate readings and have also performed an RR test on it using the DAQ card.

Could you please explain your point on the Input impedance of 6008. I did not quite understand when you mentioned that relating to the DAQ. I have tried other analog channels, to rule out the possibility of a particular input port not working.

Thanks for your quick response. Eagerly waiting for your suggestion on the same.

Many Thanks,

Manju Sharan

[Brian_Beal]

You really need a signal conditioner for this.  If you are using the +/- 1V range, at best, you will be able to resolve about 0.5 mV. If you are using 10VDC for excitation, then at 100N-m, the sensor will be outputing 15mV.  You should be getting some intermediate readings, but they would be very inaccurate.

[07875193382]

Hello Chris and Brian,

I have rectified the issue and DAQ 6008 is detecting the intermediate readings now. I had set the maximum and minimum limit as 10 V, (Input Voltage detetction) which was the prime reason for this behaviour.

Thanks Chris and Brian for your time.

Manju Sharan

[Canok10]

ok. What did you do as a change?