EcoMonitor - Air Quality Continuous Monitoring System

Author(s):
Jose P. Caetano - INESC
Victor F. Dias - INESC
Pedro A. Alves - INESC
Ricardo J. Jesus - INESC

Industry:
Pulp/Paper

Products:
LabVIEW

The Challenge:
Automated continuous monitoring of exhaust gases produced by boilers and industrial furnaces in a pulp and paper factory

The Solution:
Developing an open, user-configurable client-server system using DAQ and SCXI products controlled by LabVIEW.

Introduction
Because of environmental legislation in Portugal, companies releasing gases into the atmosphere must have a continuous-monitoring system to measure emitted gases and execute periodic reports to the authorities. Portucel, one of the major paper companies in Portugal, contracted with INESC, a member of National Instruments Alliance Program, to install a new system in one of the oldest pulp factories in the country.

EcoMonitor
The goal of this new independent system was to acquire, transmit, process, archive, and visualize the required signals, as well as to build automatic reports. Portucel wanted a central computer inside the main building to:

• Monitor all signals measured
• Implement a database
• Produce the periodic reports to the authorities

There were three emission sources - two boilers and one furnace. They were located around the factory at distances up to 200 m from each other and 400 m from the main building. Sensors for measuring the physical phenomena were already installed, with readily available voltage or current signals. They wanted all software and hardware to be based on open standards and readily expandable; they also wanted to have in-house autonomy to manage the system. Other system requirements were (1) monitoring and controlling the calibration of several sensors, (2) built-in security levels, and (3) data transfer between the new system and an existing IBM AS/400 mainframe.

We chose a client/server approach with two levels of hierarchy. At each of the three emission sources to be monitored, we placed an EcoMonitor Remote station that acquires data from the sensors 24 hours/ day, and monitors and actuates the calibrations on the sensors. The EcoMonitor Server:

• Manages communications to the three remote clients
• Processes and archives data in a database
• Provides a "real-time" graphical view of the system
• Automatically generates reports in Microsoft Excel

LabVIEW was chosen as the development software not only because of its unique capabilities to acquire, process, and visualize data, but also because it has the required data transfer capabilities (TCP/IP, SQL, OLE), programming and debugging simplicity, and concurrency between processes. One of the major problems encountered in this application was the need to execute parallel tasks, such as communications, data transfer, and data visualization.

We took advantage of the flexibility of SCXI along with the ease of data acquisition programming with LabVIEW to build a monitoring system that is powerful, flexible, and expandable for the future. Voltages and currents are conditioned and digitized inside the SCXI chassis to avoid interference from the industrial environment.

EcoMonitor Remote
An EcoMonitor Remote system consists of a Pentium 100 PC with 32 MB of RAM, running Windows 95. The software application is a LabVIEW executable built with Application Builder. Interfaced to the PC via the parallel port, a single SCXI chassis houses an SCXI-1200 multifunction DAQ module, an SCXI-1122 module for analog signal conditioning, an SCXI-1162HV to watch for sensors calibration, and an SCXI-1163R to actuate manual calibra-tion. These SCXI conditioning modules are all isolated to prevent damage by electrical discharge.

The two main tasks of EcoMonitor Remote are (1) continuous data acquisition and (2) calibration watch/actuate service. Besides these main tasks, it performs data averaging and transmission to the server, DAQ system configuration if ordered by the server, and UPS management in case of power down. The data acquired is always saved to the disk to prevent loss during power down. We implemented a floppy disk transfer as a backup during a communications network malfunction.

EcoMonitor Server
The Server is a Pentium 166 with 48 MB of RAM, running Windows NT Server 4.0. The application runs inside LabVIEW without the diagrams. The main task of the Server is to run several services available to remote stations and to the user interface. The services are communications, database access, the alarms server (receive, display, and archive), time server, and UPS management. Data transfer between the Server and the AS/400 main-frame can be done manually or automatically. All communications are based on standard TCP/IP under Windows. Automatic reports are generated in Microsoft Excel, through the OLE Automation Server VIs. We are able to provide the reports required by the legislation, as well as exploit the flexibility of Excel for customized data processing. The database is implemented with Microsoft Access, interfaced through the LabVIEW SQL toolkit. We consistently use Microsoft applications to cut down overall costs.

The data visualization panel displays valuable information about the emitted gases. The window displays the data along with signal limit values. The data plot changes color if the limit is exceeded. The user may also choose to see data automatically updated. The data visualization and alarm management panels are most frequently used; they both run in parallel with the Server application.

Conclusions
This application was technically challeng-ing in many ways. Every function, client and server, are implemented using LabVIEW, with a small exception of one CIN (Code Interface Node) used in the Server. Because of the simplicity of building the user interface with LabVIEW, we were able to discuss functionality details early in the project development and provide the customer with the solution he asked for.

LabVIEW also proved its suitability for large applications. The EcoMonitor Remote has 39 VIs (1.71 MB of code) plus 36 from the vi.lib. The Server has 185 VIs (19.4 MB of code) plus 28 from the vi.lib and has 28 front panels. These metrics were obtained with the LabVIEW Professional Developers Toolkit.
After a one-week course about the system operation, the customer was fully capable of managing and even expanding the system to monitor more signals. In the future, remote units can be placed far away from a computer and communicate through RS-485, for example, with no significant software changes because all the communications are based on the Windows network standard.

For more information, contact:

Pedro Alves

INESC - Instituto de Engenharia de Sistemas e Computadores

R. Alves Redol, 9 - Apartado 13069

1000 Lisboa, Portugal

Tel 351 (1) 3100235

Fax 351 (1) 3100316

E-Mail pedro.alves@natinst.com, http://analog.inesc.pt

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