LabVIEW not detecting DAQ USB6009

[Annabelle]

Hi,

A short introduction. I am having my internship in Australia where I am doing a project whereby thrust produced by the propeller has to be measured. From much research it seems that an option is to use a load cell and then getting readings from LabVIEW. However, I am very new to LabVIEW and even propellers (also my first time posting on a forum) as I am not an Aerospace or Mechatronics undergraduate but and Electrical student. I faced some problems while trying to test for thrust as below: 

1) I have connected the circuit from load cell to instrumentation amplifier module to the NI DAQ USB 6009. I am not sure if my connections are correct. I have attached pics of how I connected, the schematic of the Instrumentation Amplifier Module and the pin that the WheatStone Bridge would be connected to on the Module.

PIN 1: Output to DAQ

PIN 3: V- 

PIN 4: V+ (Power Source of 10V)

PIN 5: GND

PIN 7&8: Excitation Voltage

PIN 10: Wheatstone bridge V+ 

I connected JP6 which is 10V for Excitation voltage and JP1 for 1000 gain range.

This is the link to the load cell that Im using, with the wire colour code: http://www.process-controls.com/intertechnology/Revere_Transducers/pdfs/BSP.pdf

Could I also ask what is the Shield wire (transparent) for?

2) With this circuit connection,  I tried LabVIEW. However when I click the 'Force(bridge)' choice, it shows that 'no supported devices found' (as shown in attached pic1) as many Youtube video chose force when dealing with load cell. But when I tried 'Strain', it showed my device an its Analog input choices (as shown in attached pic2). Is this because there is a connection error in my circuit or are there any other reasons for this? 

3) When I tried 'Strain' and continued on to add DAQ Assistant and filling up the configuration section (as shown in attached pic3), there was no 'Device' beside 'Settings' which was different from all the videos i saw from Youtube. Is it also due to circuit fault or is there anything that I have not done.

4) Downloaded the DAQmx driver and opened NI MAX to check whether my DAQ was detected and all was good, LED blinking, however when the test was ran,the graph showed negative voltages when it should be 4.5V or so. Is my DAQ faulty?

I would gladly appreciate any replies as I am so confused and lost that I do not know how to continue on with measuring the thrust and its my first time getting in contact with all these.

Thank You!

[GerdW]

Hi Annabelle,

However when I click the 'Force(bridge)' choice, it shows that 'no supported devices found' (as shown in attached pic1) as many Youtube video chose force when dealing with load cell. But when I tried 'Strain', it showed my device an its Analog input choices (as shown in attached pic2). Is this because there is a connection error in my circuit or are there any other reasons for this? 

Why do you think you can use any of these two modes (Force and Strain) when you just want to measure an analog voltage with your USB6009? Use a simple voltage measurement!

(Hint: start with any of those simple example VIs for DAQmx Voltage readings.)

Quick check1: use a small battery (type AA or similar) and measure it's voltage using AI0 of your USB6009. Does the the reading make sense?

Quick check2: use a potentiometer (~20k) and connect its endpoints to +5V and GND of the USB6009. Then read it's output using AI0 while turning the pot. Does the reading make sense?

[Bob_Schor]

Annabelle,

     Following up on GerdW's usually excellent response, I believe that there are specialized NI Instruments that are designed to make Bridge measurements, as well as directly measure temperature, strain, frequency, position, etc.  The USB-6009 has Analog Voltage Inputs and Outputs, Digital (TTL) Inputs and Outputs, and a Counter -- any other "derived" measurement (such as force, current, etc.) needs some external circuitry (ask an EE student) to transform the quantity into a voltage in the ±10V range of the 6009.

Bob Schor

[Annabelle]

Thank You very much for the advice and I managed to get the Voltage readings. However my next question is how to display Thrust(force) instead of Voltage against time? Is there any way to do this? As I would in the end need the data for thrust.

[Annabelle]

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Bob_Schor,

I tried going to 'Find Examples' and found the Bridge- Continuous Input.vi (as attached pic1), however when tried to run, Error 200431 appeared (as attached pic2). 

Are there any other way to solve this error without changing of devices?

[RavensFan]

You get that error for the same reason you couldn't pick the device.  A USB-6009 does not support strain measurements.

Look for NI devices that do support strain measurements like the NI-9237.  http://www.ni.com/en-us/shop/select/c-series-strain-bridge-input-module

Or use the instrumentation amplifier and set up a voltage task.  Create a scale so that you can convert Voltage to Load based on the specifications of the load cell and the amplifier.

[Annabelle]

Hi RavensFan,

Im sorry but is it possible if u provide a more specific procedure on how to do this as I do not quite understand?

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@RavensFan

Or use the instrumentation amplifier and set up a voltage task.  Create a scale so that you can convert Voltage to Load based on the specifications of the load cell and the amplifier.

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Our supervisor is not providing much help and we urgently have to get the thrust against time for him in order to continue with the project whereby left with only 1 month to the dateline. I really apologize if questions I ask seem easy and obvious as I really am lost as we are running out of time.

Thank You! 

[GerdW]

Hi Annabelle,

simple, quick&dirty solution: use simpe math functions to apply the needed scaling to your voltage values.

DAQmx solution: setup a DAQmx scale using the DAQmxCreateScale function, then wire the scale reference to your DAQmxCreateVirtualChannel function. (This is a very good resource on DAQmx.)

[Bob_Schor]

As I tried to explain, to directly take a Full Bridge Measurement, you need hardware capable of doing this.  Now, if you had an NI 9237 four-channel simultaneous bridge module connected to your system (probably through a CompactDAQ device, it would show up in MAX, you could configure it for Full Bridge, and the example would probably work.  But if all you have is a USB 6009, reading Volts, it will not have the specialized Inputs and Outputs necessary to make the Bridge measurement, and LabVIEW will politely inform you of this with an Error Message.

Bob Schor

[Bob_Schor]

I have a triaxial Accelerometer that I can hook up to my USB-6009.  It outputs three voltages corresponding to X, Y, and Z accelerations.  According to the Data Sheets, the offset (voltage when the acceleration is 0g) is 1.5v, and the gain (volts per "g") is 0.3.  Of course, it also says that these are nominal values, ±10%.

So some students hooked these things up and got readings of 1.591v, 1.612v, and 1.901v (actually, I just did this, myself, and these are the readings I got).  What does this mean?  If we subtract the "nominal" offset of 1.5v, we get 0.091v, 0.112v, and 0.401v.  Dividing by 0.3v/g, we get (roughly) 0.3g, 0.4g, and 1.3g,  As it happens, I know the "right answer" -- the Accelerometer is lying with the Z Axis "up", and is not moving, so the "correct" values are 0g, 0g, and 1g.  Can you say "Calibration"?

So you have Voltage from some gadget, and you want "Thrust".  I don't know what you are measuring, how the physical variable (acceleration, in my case) gets transformed into Voltage, so I can't advise you in how to transform the Voltage back into the underlying physical variable.  Just watch out for the "constants" or "conversion factors" in the Formula, and make sure that you have some means to testing/measuring/computing them.

For Extra Credit, how would you calibrate my Triaxial Accelerometer?  If I do calibrate it and again take readings with the Accelerometer flat and unmoving, I get 0.003g, 0.014g, and 0.997g, much more reasonable values.

Bob Schor