I need to automate the control of a gas carburising furnace. The available signals are Thermocouple K-Type (4 nos., one each from the three zones and one from the geometrical center of the furnace) and Oxygen Analyser. That makes it a total of 5 signals, all available in RS-485 format, which I need to acquire (10 samples/second) and then initiate a control action as per the rule base. Reliability is a major issue and the system has to work in harsh conditions. What hardware would suit my purpose? I would prefer NI hardware which can be programmed via VB or VC++. LabVIEW may be considered as the last option. Apart from using the thermocouple/Oxygen analyser signals for controlling it is also desired to store them on a PC for analyses and visualisation (via graphs etc etc) My need is URGENT and would appreciate any help. Thanx in advance Gurdas
We would really need one more key piece of information about your sensor. You mention that the thermocouple signals are available through the rs-485 format. To me, that must mean that you already have some type of device that converts the millivolt thermocouple readings to serial information that can be retrieved by a controller on a rs-485 bus. Or to be more specific, you must be using some sort of industrial hardware, such as a Remote Telemetry Unit or PLC to convert these thermocouple readings to rs-485. However, your industrial hardware should also specify some form of communication protocol that it uses over rs-485. This protocol is what describes the commands that are sent/received over the rs-485 bus to talk to your device, and this will therefor e determine the interface software on the computer. For example, two common protocols used with rs-485 communication are Modbus and Optomux. Therefore, the computer would need software that could "speak" this protocol (such as Modbus or Optomux) over rs-485.
On www.ni.com, we have a KnowledgeBase titled "Drivers for Communicating to PLCs, RTUs, and Other Industrial Hardware" that provides an excellent overview of the software interface to VB, VC++, and LabVIEW for this type of industrial communication. Here is a link: