This tutorial provides an overview of a bag tester automation project designed by HIATRONICS. The tester runs a bag inflation and burst test for testing the bust pressure of bags. The application uses the following methods and techniques:

• Asynchronous PID Rate Control
• Maximum Value Instrument Monitoring (for burst detection)
• Volume Integration Instrument Value
• HTML Parameter Setting
• Asynchronous Instruction Display
• Rapid Fill Pneumatic Circuit

Test Description:

This bag burst tester design offers significant advantages over current bag burst testers.

This machine allows for rapid bag inflation during the initial fill. Bags of any size can be tested using the same settings. There is no need for operators to need to choose test settings for every test, because the controlled fill and burst PID would allow any bag size to increase its pressure at the same slow pressure rate (say 0.1 inH20 per second) for all bag volumes.

Asynchronus Rate Control: This tutorial simulates the real bag burst tester in real time using a NI-USB 6008, and popping a bag is simulated by physically shorting an instrument channel during the test.

For this tutorial a method within the PID object called 'AsynchronusPidRateControl' was used. This method only sets the PID's starting, ending, and rate. Then the PID rate is automatically updated in parallel to the test sequence using the system's ping event.

After the AsynchronusPidRateControl method is called, the test sequence immediately goes to the next step, in which instrument 1's value is monitored. During the monitor method the instrument's rate keeps increasing until the bag pops. Within the monitor method, the peak pressure is continuously updated, and when the bag pops this value is retained. This monitor method can not detect when the bag pops, but instead uses this peak pressure to measure the maximum pressure that was attained during the method. This monitor method does not end until after the bag deflates and the pressure falls below say 1 inH2O.

Within the test sequence you can achieve all of this with just two lines of code.

Setup Instructions:

This application used a National Instruments USB-6008 data acquisition board. Note that any compatible board could be used as long as the DAQ board which is used is selected within the application’s tree view.

The application’s channel wiring was as follows:

• AI0 directly wired to AO0
• AI1 directly wired to +5V
  • you could also wire this channel to a voltage divider to provide lower voltage (say 1 or 2 volts).
  • you could also wire this channel to AO1 and then create an actuator, in order to provide small voltage to this channel.
• To simulate the bag popping, simply touch a wire connected to the board's ground to the AI0 channel to drop the voltage.  This should be done during the time in which you are waiting for the bag to pop.

Project built from: NONE

Downloads: Pneumatic Diagram & Pressure Vs Time Sketch