Laboratory Data Acquisition
The Challenge: Monitoring, displaying, recording, and reporting data previously plotted on a multipen Chessell strip-chart recorder.
The Solution: Developing a LabVIEW-based SCADA system that uses the NI Modbus server to acquire data from the recorder serial port.
A large chemical company identified the need to improve a critical temperature and relative humidity (RH) monitoring system in a production QA Lab at the Bound Brook, NJ plant during September 1997. The existing system consisted of a Eurotherm Chessell paper strip-chart recorder, which received the data from RTD probes in several ovens, a density column bath, and room air temperature and RH sensors and plotted it with a three-color ink cartridge.
Paper jams, which had become a regular occurrence because of variations in paper consistency and the age of the Chessell instrument, made it difficult to monitor the inputs without interruption and loss of data.
When a critical variable went out of tolerance, a significant amount of time could pass before an operator discovered and corrected the error. Then the operator had to conduct an investigation and write a lengthy corrective-action report. Archiving the paper also presented a problem because the ink faded over time; the archived charts were difficult or impossible to read. Of course, operators could never extract data off the strip-chart recorder to plot on a computer or incorporate in printed reports.
Process Automation was contracted to replace the data presentation functions of the strip-chart recorder with a PC-based SCADA system using LabVIEW from National Instruments. Goals for the new system were to:
- Bypass the paper charting system
- Reduce the number of corrective action
- reports through improved monitoring
- Make the storage and retrieval of data an easier task
- Data retrieval from the IA server into its real-time database
- Alarm monitoring and reporting
- Automatic data/time spreadsheet report generation
- Historical data compression and archiving
- Data trend plotting and printing
Because of the ease of development and the flexibility of LabVIEW, along with the “jump start” provided by the TrendSafe-SCADA®, we implemented the new system in only eight days. The upgrade dramatically improved data acquisition and analysis, made out-of-tolerance readings much easier to identify, and helped minimize the number of corrective-action reports for the lab. client personnel were pleased beyond all expectation with their improved monitoring capabilities.
With the LabVIEW-based system, laboratory personnel have estimated that they save approximately two weeks of downtime per year previously spent attempting to recover lost data and writing extra reports.