Network-based control, monitoring and calibration of shipboard sensors

Abstract

The objective of this thesis is to develop a new calibration system for analog and smart digital pressure sensors, operable by only one person, and capable of calibrating local and remote sensors connected via RS232 cables, Bluetooth or an 802.11b wireless LAN. It is proposed that the operator uses a portable calibration standard and a tablet PC to conduct the sensor calibration. In order to handle local sensors directly connected to the tablet PC and remote sensors connected to the tablet PC via a network capable application processor (NCAP), a dual module application is proposed and developed using LabVIEW. The application has a Master Module and a Slave Module. Both modules are able to connect to multiple digital sensors at the same time. The Master Module was designed to run on the operator's tablet PC offering an easy-to-use graphical user interface (GUI) that allows the monitoring or calibration of any connected sensors. The Slave Module was designed to run on any networked PC, including the operator's tablet and an NCAP. A dedicated Virtual Instrument (VI) was designed for an iterative calibration process based on a least squares fitting method. This VI automatically computes the calibration constants that minimize the measurements errors, and writes the calibration constants to the sensor's RAM or EEPROM. A prototype shipboard sensor test bed was constructed in the laboratory, which consists of a Honeywell PPT digital pressure sensor, an Omega analog pressure sensor, and other 802.11b and Bluetooth wireless LAN components. The newly developed calibration system was successfully demonstrated.