ICP (IEPE) Load cell data aquisition with external excitation source

[meetgsl]

I am working towards aquiring data from a Peizoelectric force sensor ( ICP ) with 0-5v output and its own constant current excitation.

Please suggest recommended DAQ devices for such transducers. (We usually use PCI (6229) or compact DAQ (9215) devices for static load cells.)

Additionally, from LV point of view, is the process for aquiring AI signal from such ICP force sensor different than static load cell with 0-5v output?

your thoughts?

[Jason_D]

meetgsl,

You could look at something like the 9219 for a universal type module that will work with many different types and offer simple isolation and other common benefits to these types of measurements.  Does your application require anything specific other than just AI?  Do you have accuracy concerns?  If not it sounds like pretty much anything will work.

[meetgsl]

Thank you Jason for your suggestions.

Let me elborate more on the application. I am trying to measure the impact force in drop weight impact test. So to capture this impact force using ICP force sensor requires very high data aquisition rate. I am using 100 Khz.

I am using 9215 with 104ks/s/ch with channel to channel isolation. I dont know much specifics on the output of the ICP force sensors. The manufacturer of the force sensor specs out 0-5 volt output spanned across 0-50k lbf. 

I am wondering if such sensors requires any specific settings from DAQ point of view. 

I have the ICP constant current excitation provided by the signal conditioner supplied by the force sensor manufacturer. The output from this signal conditionaer with unity gain (BNC connection) goes to 9215 with open wire connection on Ai1 on DAQ board.

I am reading this channel using AI 1D waveform Nchannels Nsamples using a task defined in MAX with AI voltage in differential config.

Please share your thoughts on this configuration.

[Jason_D]

meetgsl,

You will probably want to implement a custom scale with your task to change the voltage to your units.  I can't think of any other suggestions for you.  Are you getting good results?

[meetgsl]

Thank you jason for your reply.

I am getting good signal from 9215 with custon scaling implemented in MAX task. I've posted this thread to make sure i m acquiring data using best possible NI DAQ software and hardware. 

if you thing that i am doing everything fine then i would like to implement some sort of signal conditioning and features to get smooth signal out of the force sensor. 

Are there any specific filtering VI's avaialble to a signal from such ICP force sensors with only one peak. How do i go about getting a clean signal and condition it to reduce/eleminate noise.

Here are some specific questions. 

1) Save and display the waveform part including impact peak only. 

2) Write impact peak data only.

3) Display peak impact force.

4) Display the pulse width of the impact peak.

5) Signal conditioning -- can i import a txt file of a typical signal from ICP force sensor and perform a FFT to determine low and high pass frequency values to condition waveform to reduce noise.

These are very specific questions and i m sure there must be something readily avaialable in LV to accomplish these tasks.  please guide me to right location for the purpose.

Thoughts/suggestions/recommendation?

Rgds

Meetgsl

[Jason_D]

meetgsl,

Before I start into specifics I believe that in general you will want to go into the functions palette Programming»Waveform and more specifically Analog Waveform»Waveform Measurements.

1)  This depends slightly on what you want to be your entire peak, ie how much data on each side of the peak do you want to keep.  I would suggest that you use either the Waveform Peak Detection.vi or the Search Waveform.VI to detect the peak.  If you want to vary how much data around the peak you keep you could use the Pulse Measurements.vi or the Transition Measurements.vi to determine how fast the peak rose and keep a certain amount of that data.

2)  The VIs described above will either give you back subsets or times when something happend.  You can use the Get Waveform Subset.VI to set a start and end time and only export the signal you need.

3)  Either use the Waveform Peak Detection.vi as above or the Waveform Min Max.vi for a single peak.

4)  Use the Pulse Measurements.VI

5)  Use the FFT Spectrum.vi as far as importing a signal that should be fine but I am not exactly sure how you are looking to do a comparison with that signal.

[DAQ_G]

Jason,

Thank you for your recommendations, I will try n implement them and then send you the final VI.

I've got the NI 9233 module with IEPE excitation. Now I am trying to see if i can use this guy to set AI task for my ICP force sensor with 0-5volts out for 50k lbf.

Now how do i set the task in Max?

I tried using the Acceleration task with IEPE. I am not getting how to setup task to read AI from force senor. Please suggest reccommeded process for ICP force sensor.

Thanks

Meetgsl

[Jason_D]

DAQ_G/meetgsl, (I guess DAQ_G is your "secret" profile or something )

I would suggest using a Custom Voltage with Excitation task and then as I mentioned above using a custom scale to change the voltage into lbf.

[GaneshSL]

Thank you Jason. DAQ_G is my office profile and the other one i use it at home.

I have got a very good signal out of NI 9233 IEPE excitation as compared to the one provided by ICP force sensor manufacturer.

I am looking into getting one this for my test stand. Please suggest IEPE excitation BNC with at least 100ks/s/ch.

9233 and 9234 are kinda limited with thier 51 ks/s/ch.

Thank you for your support.

[Jason_D]

GaneshSL,

The 4432 or 4431 should be exactly what you are looking for.  Be aware that all of the 9233, 9234, and the 4432 are DSA devices which are not the same as a regular M-Series devices.