How would I use Labview to determine the pressure inside a suppressor?

[jenifr2g@cox.net]

My company just purchased Labview about a month ago. Nobody here has ever had any experience with the application. In the last week I have been going through tutorials and reading up on it. Now I have been told I need to get everything set up before Christmas break so that we can test a suppressor for one of our guns for a client. The main goal is to determine the pressure inside the suppressor once we fire a gun. We have done a couple of experiments before in determining the pressure inside a suppressor but with a different software, one that's not as accurate. About 2 months ago in the meantime while waiting for your product we purchased a strain gage box which is very simple to set up and run known as Pressure Trace II. Using this product we attach the strain gage to the suppressor in 2 different locations and after hitting run on the computer it gives a graph of the strain over time until we hit a stop button on the computer. Given strain we determine the pressure using engineering methods.

Now that we have your product we want to test the suppressor again to make sure it wont fail when fired. So, my question would be, are there any examples as to how I would set up Labview in order to determine the pressure inside a suppressor when firing a gun? I would want Labview to start acquiring data as the gun is fired and stop when the bullet exits the suppressor. Can you be of any help? Thanks

[ssk]

You will need some kind of hardware to get the signal into the computer that suits the output of your transducer. Does your existing starin gauge box have any outputs on it (analogue, serial - RS232 or 485, GPIB etc)?

The application sounds relatively straight forward.

[AdnanZ]

Well, first we need to figure out how you are going to communicate with the suppressor using LabVIEW. Are you planning to purchase DAQ devices from NI that can perform strain gage measurements or do you want to keep using the Pressure Trace II instrument? If you are thinking of using the latter, then how exactly do you communicate with that instrument from your PC; is it using USB, serial or any other communication protocol?

[jenifr2g@cox.net]

We did purchase DAQ devices from NI. We also purchased a front-sealing high pressure sensor suitable for all ballistic pressure measurements from 100 to 6000 bar. Basically we are going to attach the purchased sensor to the suppressor barrel and we will have it hooked up to a dual mode amplifier, also purchased from KISTLER, which will then be connected to the labview box. Basically all I am looking for is how to set up labview so I can obtain the pressure inside the suppressor. I need to figure out how to set up the front panel and block diagram to give me the pressure inside the suppressor as the gun is fired up until the bullet leaves the barrel. I have no clue how to go about doing this.

[AdnanZ]

Unfortunately, nobody will be able to provide you with the right application to get this up and running since we don't know what exactly the hardware is and generally won't develop applications from scratch. I would recommend that you go through the following tutorials:

How Can I Learn LabVIEW?
Getting Started with NI-DAQmx

and also going through the DAQmx examples that are available in the Example Finder. You can navigate to this by going to Help -> Find Examples in the LabVIEW environment.

Also, if you want more help, be sure to provide info on all of the hardware that you are using in this system including NI products. I would recommend that you get trained with using NI products, but since you don't have much time, the above suggestions should help you get up and running.

[jenifr2g@cox.net]

Ok, the exact way this will be working is as follows. We will mount a sensor from KISTLER known as Type 6215 on the suppressor. The sensor information is attached in a pdf shown below known as 6215 manual and pressure model 6215. Basically the sensor is a piezoelectric pressure sensor. It measures pressure accurately and precisely over a wide range, even under extreme conditions. The range of the sensor is +/-10V. This will be connected to a charge amplifier purchased from KISTLER known as Type 5010B, mainly to reduce noise. Basically this amplifier converts KISTLER sensor signals into proportionally controlled voltage. The pdf with the information about it is attached below in a pdf known as 5010B dual mode amplifier. This amplifier is attached to the BNC-2110, purchased from NI, which is an accessory for multifunction E series, S series and analog out device which is connected to the chassis purchased from NI. It is a "shielded connector block with signal-labeled BNC connectors for easy connectivity of your analog output, digital I/O and counter/timer signals to your multifunction DAQ device, including analog output devices". The chassis purchased from NI is known as the PXI-1050. The PXI-1050 chassis has the PXI-6123 (16 MSamples) S series multifunction DAQ device installed in it. Information about the DAQ device is given in the pdf known as PXI-6123 attached. From here the information gathered is sent to the PC.

Here is an outline of how I would like to set up my code in labview but am unsure as how to do it:

I would like to have an arm switch to turn the program on and off. I would like to have my output a graph of voltage vs. time. I would also like to have constants in there that would affect the graph. I want the constants to be as follows:

MU/V, which would be the measuring unit per volt that I would input, and a trigger level, such as recording data on the graph once the pressure in the suppressor reaches 20psi, and I would like to be able to have a time interval as a constant. So I would want a total of 3 constants.

Therefore, x and y would be dependant on my constants.

I would also like to have labview tell me the max pressure reaches and at what time it occurs. 

Do you know if all of this is possible? If so, do you know of any examples that have a similar setup? Or would you know how I would be able to set this up?

Adnan Z, thanks for all of your advice and thanks for reading my question. I greatly appreciate it.

[jenifr2g@cox.net]

I am sorry, I meant I would like my output to be a graph of pressure vs time, not voltage

[jenifr2g@cox.net]

Ok, I was confusing myself. It is voltage vs time that I would like to plot, not pressure vs time. So I was correct with my first statement. But, once I graph voltage vs time I would like to set something up that would transfer the voltage to pressure if possible.

[Now_With_Underscores]

Hi Jenifr,

I like you're application!  What gun and what suppressor are you testing? 

As far as your application is concerned, I would highly recommend taking a look at our free online tutorials on LabVIEW that can be found at https://learn.ni.com/learn/article/labview-tutorial.  If you are interested in hands-on classes with an experienced LabVIEW instructor, navigate to https://www.ni.com/en-us/shop/category/courses.html .  You can also view examples in LabVIEW by going to Help >> Find Examples.  Once the example finder opens, double click on 'Hardware Input and Output,' then 'DAQmx,' then 'Analog Measurements.'   Now select the specific measurement you're looking for.  Since you have an external 3rd party device that outputs a voltage, we are going to perform a voltage measurement.  Since you want this to trigger on some start condition and stop after a certain condition is met, I would recommend taking a look at the 'Acq&Graph Voltage-Int Clk-HW Trig Restarts' example (in the 'Voltage' folder).  You could set your trigger (the signal that starts your signal) to be a button that is activated when the action of the gun releases, or we could continuously acquire and then select a certain number of samples after the voltage reaches a certain level, as in 'Acq&Graph Voltage-Ext Clk-Analog Ref'.  In this example, we continuously acquire samples and save the last N samples (called 'pretrigger samples'); once the trigger occurs (voltage exceeds 0.34211 volts, for example) we keep the last N samples and then acquire M more samples. 

If you use one of our DSA boards (for example, the PXI-4462), then we can provide the excitation with our high precision board and correctly scale the returned signal based on the excitation voltage.  Since you're using a 3rd party device to convert to a voltage, we will need to use a custom scale to get your voltage returned to the corresponding pressure value.  Our online KnowledgeBase and Developer Zone articles provide information on how to configure common user applications.  For example, in order to find information on how to scale voltage to pressure, go to ni.com and then search for "What Are Custom Scales, and How Do I Use Them".  This will pull up a KnowledgeBase outlining the general setup procedure. 

I will say that without any formal LabVIEW training the code will be hard to manipulate until you understand the basics of LabVIEW data flow.  Again, I would recommend the free tutorials at the very least to understand how LabVIEW operates.  Also, the context help is very useful for finding out what VIs in your code do.  You can turn the context help on by opening LabVIEW and going to Help»Show Context Help.  Getting this project under your belt will set you well on your way to understanding how LabVIEW operates.  Even if you don't have time to take a LabVIEW class before this project is due, I would highly recommend that you take one afterwards to get a solid foundation on how our environment functions. 

Message Edited by Knights Who Say NI on 12-11-2008 02:40 PM