Multi-Site Automatic Temperature Control System

Real-time Diagnostic Computer Display

Vektrex implemented a real-time, high-speed temperature control system for a Pick and Place IC Handler, that provides a minimum effective control rate of 1.6KHz and true measurement determinism. The system controls the temperature of up to eight devices simultaneously, with a precision of + 0.1 °C. The controller can perform controlled temperature slews at rates over 10 °C/second over a temperature range form 25 °C to 120 °C.

Expertise Used

National Instruments PXI Controllers in tandem with LabVIEW Real-Time provide the basis for this solution. Other technologies include high-speed analog input, analog output, digital I/O, TCP/IP communications for data logging and performance monitoring, and RS-232 for process control. The system’s real-time FIFOs assure deterministic data.

LabVIEW Real-Time

The LabVIEW Real-Time software running on the PXI chassis is broken into modules. Each module is coded to run asynchronously in its own thread/loop and assigned a priority. Modules with the highest priory (i.e., Thermal Control) run when required, assuring priority tasks are deterministic.

The Vektrex Metamorphosis™ Development process minimizes development time. Software engineers identify modules early, and then design the data interfaces between these modules first. This provides the engineers a known and comfortable environment in which to develop their module. Since each module runs asynchronously in a separate thread, developers code, test, and debug the modules independently with "real" data.

Software Modules

Pseudo-Real-Time Remote Data Logging and Performance Monitoring

A challenging project requirement is the need for pseudo-real-time remote data logging and performance monitoring. Specifically, the system must be capable of sending pseudo-real-time data to remote computers without adversely affecting temperature control. The communications system/protocol that implements this must be fast, reliable, and tolerant of improper shutdowns. 

After experimenting with National Instruments DataSocket technology and National Instruments LabVIEW TCP/IP communication primitives, Vektrex determined TCP/IP to be the best choice. TCP/IP is advantageous for several reasons. First, it is fast, and it contains built-in error checking (packets arriving out of order, after traversing a null patch cable or hub, are not a problem). Second, with the PXI chassis set to listener, it is tolerant of operators plugging and unplugging Ethernet cables at random. Finally, National Instruments supplied a VI that automates the process of remotely determining the IP address of the PXI chassis.

This project was presented at the Southern California National Instruments Technical Symposium 2002. The presentation is available in the  Vektrex Knowledge Base.