The legacy test system involved control with an Allen-Bradley PLC. The PLC was programmed almost 20 years ago, and the client had no in-house knowledge of the software. Essentially, the system was a black-box that they could not support internally. The client did, however, have experience in LabVIEW programming for Windows, and wanted to leverage it onto a new platform.
The core of the system was control of the environmental chamber. DMC reverse-engineered the control logic based on available PLC code and a strong understanding of control systems. We developed and implemented an improved control algorithm. This controlled the existing chillers, heaters, and humidifiers in the walk-in environmental room. To capitalize on deterministic and round-the-clock operation, the control algorithm was deployed on a National Instruments cRIO running LabVIEW Real-Time.
The Test Interface was programmed to run on a PC. The room control screen allowed for varying control of the environmental chamber in accordance with test requirements. A data acquisition configuration screen was created to manage input signals and scales. A sample and test configuration screen allowed sample-specific information to be input, where it becomes a permanent part of the acquired data file.
Power measurements were achieved with external transformers and transducers. From this, voltage, current, power, and energy (kWh) were collected for analysis. Other signal types included temperature and relative humidity (RH). To cover all required inputs and outputs, EtherCAT was used to connect the primary cRIO to a secondary chassis.
Ultimately, the client received a fully automated electrical appliance test system improving the level of control of the test chamber and the integrity of the collected data. Additionally, the system was developed in a single platform (LabVIEW) that was deployed to both PC and Real-Time targets. The Real-Time component provided a robust replacement to the unreliable and unsupported PLC system. The PC component provided user-friendly configuration and test interfaces. Another great benefit is that the client has full control of source code, with the ability to make future changes as needed.