PC Based Control, Monitoring system for Environmental Chambers

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PC-Based Control and Monitoring system for Environmental Chambers

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The Challenge:

Developing a PC-Based real time control and monitoring system for temperature of a Environmental Chamber and temperature and Humidity of a Humidity Chamber and publishing acquired real time data over intranet.

The solution:

Using Field Point Ethernet Module, Field Point Thermocouple Input Module, Field Point Analog Output Module, Field Point Analog input module, Field Point Digital input module, Field point Digital output modules, personal Computer, Serial Link between PC and Field Point Network module, LabView and PID toolkit for LabView, Datasocket technology.

Introduction

The PC Based Environmental and humidity chamber controller consists of National Instruments’ Field Point based Hardware. Field Ethernet module is chosen to interface with PC for real time data acquisition and transfer. The internal dimension of both the environmental chamber is 750x750x750 mm and the temperature range is from –65ºC to 300ºC for environmental chamber and –10ºC to 150ºC for humidity chamber. Both the chambers consists of a fan for uniform circulation of air and uniform heat distribution. The Field point Thermocouple module provides the PC with temperature status. The humidity status is determined by Field Analog input module. The 0-20mA output provides PID control to the Thyristor fired heating circuit and Relay contacts are used to turn on the heater circuit Field point relay modules are used turn on and off the fan and panel cooler.

The software for controlling the temperature is developed using National Instrument’s graphical programming language LabVIEW. The control is achieved using National Instrument’s PID control toolkit. The software has got the facility to run the Chamber with any number of and any combination of Ramp and Soak cycle. The operator can observe the temperature trending as well as the setpoint on a graph. The data is published over the intranet so that anybody can monitor the process from his terminal. Datasocket was used for publishing data over intranet.

System Requirements

To control and monitor temperature and humidity of environmental and humidity chamber through a user defined heating cycle. It maintains the temperature at soak temperature for user define soak temperature and interval and leads to soak temperature through a user defined rate of heating. Provision for storing cycle information as well logging of the temperature and humidity information being acquired with time stamp.Provision for automatic and manual. Automatic logging starts when temperature or humidity exceeds the warning limit. Automatic logging of data continues for 15 minutes after the time temperature of humidity comes back to normal level. Monitoring of the process is from any PC over the intranet.

Hardware design

The PC Based furnace controller consists of the following hardware:

	1.	Field Point FP-1600 ethernet 10Mbps/100Mbps Network Module.
	2.	Field Point FP-TC Thermocouple Module
	3.	Field Point FP-AO-C420 dual channel Analog Output Module
	4.	Field Point FP-DO-AC240 dual channel 240VAC Discrete output module
	5.	Field point FP-DI-AC240 dual channel Discrete input module.
	6.	Field Point FP-TB-10 dual channel terminal base.
	7.	Field Point FP-AI-V10 dual channel 0-10V Analog input module.
	8.	Field Point FP-AO-V10 dual channel 0-10V Analog output module.
	9.	Field Point FP-AI-100 8-ch, 12 Bit Analog input module.
	10.	Field Point FP-AO-CO20 dual channel 0-20mA Analog output module
	11.	Field Point FP-AO-CO60 dual channel 3-60VDC Discrete output module.
	12.	Personal Computer.
	13.	Ethernet Link between PC and Field Point Network module.

Software Architecture

This PC-Based Control and Monitoring System for environmental and humidity chambers consisted of panels to allows the user to delete and select or enter new temperature cycle with facility for entering various cycle identifying parameters. It allows the user to set warning limits and set value for humidity. The cycle consists of ramps and soaks.The software rejects a thermocouple if gets opened during the on going process. User can observe temperature trend as well as other status of the on going process such as reading of the thermocouple, humidity level, alarm indication cycle status. Separate panel is provided for user to select the logged data see the logged data in spreadsheet as well as graphical format in two separate panels.

Controlling of the temperature is achieved using National Instruments PID toolkit. Ramp and soak cycles are generated by the software .The temperature is read using a J-type thermocouples which is fed to the PID vi and whose output is scaled to

4-20mA to fire the thyristor which in turn controls the power delivered to the heater. Cooling is achieved by turning the compressor on.

Separate panel are provided for viewing and taking printouts of the logged data of each thermocouple and the average separately in graph as well spreadsheet format.

Apart from process parameter logging the system logs and monitors other parameter of the component that is being tested in the chambers.

For monitoring of the process datasocket is used for publishing data over the intranet. DataSocket is a single, unified, end-user API based on URLs for connecting to measurement and automation data located anywhere, be it on a local computer or on the internet.It is a protocol-independent, language-independent, and OS-independent API designed to simplify binary data publishing.

System Capabilities

The system is capable of maintain of maintaining temperature and humidity to a high degree of accuracy. It is capable of performing automatic data logging on error conditions. It publishes measurement data over the intranet for monitoring of the process from any PC. In is capable of running any combination and number of ramp and soak cycles. It provides facility to log and view the real time data being acquired.

Results

The system gives a real time monitoring and control of temperature with enough flexibility to the user to choose required process cycle and conditions and process monitoring over the intranet.