Wiring Futek Torque Sensor to NI 9205

[nnovack]

I took over on a project building a materials testing machine, and the previous builder left me with a Futek TRS705 torque sensor and a NI 9205 DAQ board. He claims that he bought them specifically to be wired together. I've found the wiring diagrams for the sensor and the DAQ board individually, but I cannot figure out how to put the two together. I've wired all the grounds to the COM, but I am not sure how to properly wire the power and the signals. Are the power and signal a differential pair that should be wired alongside each other (AI+ and AI-)? My experience with data acquisition wiring is pretty limited, so any help is appreciated. 

[BennyBenson]

Hi Nnovack,

Based on the document provided, I believe the signal and power are going to be differential pairs. The NI 9205 will be able to read the analog voltage from the torque, but your Futek sensor requires 11-26 VDC(nominal is 12 VDC) excitation be applied in order to output the torque(strain) voltages. You can use any type of DC power supply that can supply up to 1 Watt.

Below are the pins from the data sheet, and how you'll need to wire them.

C - Torque output - Wire to + Channel 0 of 9205(terminal 1)

D - Signal Ground - Wire to COM for single ended or AI8(terminal 19) for differential

E - Power Ground - Wire to ground of 12 VDC power supply

F - Power - Wire to + 12 V DC power supply

Are you developing this in LabVIEW? If so, I can provide a simple example on setting this up.

There is also an encoder portion of this Futek device, are you also planning to use that to track the rotation?

[nnovack]

Thank you for the help. Yes, this will be implemented as part of a LabVIEW code. I was planning on using it to measure the torque, but the encoders would help a lot in keeping track of the cycles. There also seems to be a NI PS-15 24V DC power supply sitting around. Will this work to power the sensor, or does it need to be 12V DC? 

Thanks, 

Nicholas

[BennyBenson]

According to the datasheet it can take 11-26 VDC, so the 24 VDC power supply would work fine. You'll need to create a custom scale in order to scale the voltage reading to correspond to the torque being output.

You'd be better set to utilize a digital module in order to accurately read the pulses from the encoder, however if you're going at a low enough speed you could maybe get away with using the NI 9205.

How fast is this going to be spinning?

[nnovack]

That end of the machine will be running at 1000RPM. I'm using shift registers in LabVIEW to update the cycles based on the instantaneous speed currently, and it seems to work well, but I figured it may be possible to get a more accurate count from the sensor. 

Nicholas

[BennyBenson]

How are you able to get the instantaneous speed? and What do you define a cycle as?

At 1000 RPM, you'd be getting 6000 pulses/second from the encoder. So you'd need to read at a minimum of 12kHz, and you'd need to complete post processing in software in order to count the rotations.

If you used a digital module however, you can specifically create a counter task to interpret the signal in terms of frequency or count the number of revolutions.

Do you have access to an NI C series digital module? If so, what module.

[nnovack]

The setup includes two motors, each connected to their own ABB drive. Both the drives are wired together through a common DC bus. The LabVIEW program reads the speeds from the drives, and then I use those to update the cycles with the shift registers (each revolution is one cycle). Basically, it uses the endpoint method of integration to calculate the cycles based on speed and time. This method seems to be working very well, especially considering the accuracy doesn't need to be perfect when the average failures occur close to 10 million cycles, so wiring the encoders is probably not necessary. I don't believe I have access to a C-series module, and this project has already passed its anticipated budget, so wiring the sensor for torque only is probably my best solution. 

Thanks, 

Nicholas

[BennyBenson]

Ok, makes sense. Feel free to reach back out on this post if you're having trouble reading in the values from your sensor.