Design and development of LabVIEW based environmental test chamber controller

Polymer composite materials are the most sought after materials for aerospace applications in view of their superior specific stiffness and specific strength properties. However, these materials are susceptible to the combined effects of temperature and humidity. Monitoring and control of these two parameters in an environmental test chamber, within a close tolerance for a stipulated duration to simulate the service conditions on the material is an essential part of qualification procedure for composites. At the Environmental Test Facility of CSIR-NAL, hitherto only data acquisition was possible through the computer, but the control activity required the operator to move physically to access the controller and provide the necessary change in inputs. The limitations have been successfully addressed by the design and implementation of a LabVIEW based software for monitoring as well as control of temperature and humidity in the environmental test chamber. This approach has eliminated the use of the existing DAQ and retransmission module hardware and further the controller itself is used as a DAQ device facilitating the control and functionalities such as data acquisition, storage, retrieval and presentation through LabVIEW software. Further, the need for physical movement of the operator to access the controller has been eliminated. In this paper, the development of a closed loop control algorithm and data acquisition protocol using LabVIEW is presented. The LabView has been used with an iTool Modbus Open Platform Communication (OPC) server for monitoring and control of temperature & humidity in the environmental test chamber. The innovative and novel controller has made the environmental conditioning process more efficient and cost effective. The accuracy achieved using the newly developed ETC is ± 0.5°C for temperature and ± 1% RH in case of humidity vis-avis the accuracy of ± 2°C and ± 3% RH, achieved with the old controller.