Data Acquisition and Control System for Testing Beverage Vending Machines

Author(s):
Bryan Nadeau - Life Cycle Engineering Inc.

Industry:
Food/Beverage

Products:
LabVIEW, Signal Conditioning, PXI/CompactPCI

The Challenge:
Developing and integrating a data acquisition and control system for two vending machine test cells for a leading manufacturer of soft drink vending machines.

The Solution:
Using National Instruments hardware and software, Life Cycle Engineering developed and installed a high channel-count data acquisition and control system to control temperature and humidity in two test cells while acquiring, displaying, and storing up to 512 channels of analog data.

System Components
We chose two PXI-1011 chassis with four PXI slots and integrated eight SCXI slots as the foundation for the system. PXI-6030 E series DAQ cards installed in each chassis provided the necessary 16-bit resolution. MXI-3 fiber optic technology provides communication between the chassis and the PC. The fiber optic connection provides complete noise immunity and eliminates the need for PXI controllers. The use of controllers with Ethernet connectivity was considered, but we chose to use MXI-3 as the chassis would not be easily accessible, and to locating peripherals on top of the test cell (keyboard, mouse, and monitor) was not desired. MXI-3 was also the most cost-effective solution.

In order to communicate with temperature and humidity process controllers installed in each cell, we installed a PXI 8421 8 port RS-485 interface card in chassis 1. This reduced project costs by eliminating the need to run cable for RS-485 communication from the test cells to the main PC. We chose LabVIEW as the application software because of its easy integration with National Instruments data acquisition hardware, ease of use, built in serial communication VIs, and available SQL VIs. Using the Measurement & Automation Explorer, hardware setup and configuration of 512 analog channels was simple. We used the Enterprise Connectivity Toolset to an ODBC compliant database for data storage and retrieval.

All of the screens in the user interface were developed using LabVIEW 6i. The data acquisition and control screen shown below gives the operator the ability to start tests on any of the eight test stations, set the test cell temperature and humidity values, and provides links to the real-time display and report generation screens.
With the channel configuration screen the user can enable or disable individual channels, name the channels dynamically using text controls, and set the sampling rates individually.

We used DataSocket server VIs in LabVIEW to publish the raw data throughout the customer’s facility via the local area network (LAN). Remote monitoring is also possible via the Internet. A reader VI compiled as an executable is needed to access test data, and an installation CD gives the customer the ability to control access to the test data.

With a report generation screen developed in LabVIEW 6i, the customer can create customized graphical or text reports from acquired data. Test data is stored in a Microsoft Access database as it is acquired and accessed by LabVIEW. Users can also access this data via the SQL toolkit. The screen allows the user to select which test to display and gives them the ability to select the channels to include in the reports. In addition, channel names are retrieved from a test configuration table and used to label plots in the chart legend. A report generation screen developed in LabVIEW 6.0 allows the customer to create customized graphical or text reports from acquired data

Conclusion
Using National Instruments PXI and SCXI hardware along with LabVIEW 6i software, Life Cycle Engineering (LCE) developed a cost-effective PC-based data acquisition and control system. The system controls temperature and humidity for two test cells while simultaneously acquiring, displaying, and storing up to 512 analog inputs. Additionally, test data is published real-time, using DataSocket technology, throughout the company’s Local Area Network for monitoring by design and test engineers.

The PXI 1011 chassis provided ample slots for data acquisition, RS-485 communication, and SCXI analog signal conditioning modules. The use of MXI-3 remote controllers eliminated the need for locating computer peripherals above the test cells, and provided noise free communications between the chassis and the PC.
Using LabVIEW 6i simplified software development with built-in support for the data acquisition hardware and available SQL Toolkit.

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