• Libratherm Instruments Private Limited

Process Transmitter With RS-485 Interface

Libratherm offers micro-controller based Process Transmitter model PTX-3000 for measuring and transmitting the analogue and digital values proportional to the Process Input. This model can accept eight industrial standard universal inputs, which is user selectable using internal DIP switch. For input selection, three options are available, where user can specify the desired model for a) universal input or b) any of the two fixed inputs or c) any of the single fixed input. Temperature or Process values corresponding to the input is indicated on the display and the corresponding display range is converted to the 2 wire isolated current output of 4-20mA proportional and linearized to the process input. This linearized signal can be used for remote measurement and indication. For the dual input model PTX-3000-T, two independent 4-20mA signals are available on three wires. For interface with PLC or DCS or with any other process controller – the measured and displayed analog input is converted for digital serial communication on RS485 bus with MODBUS RTU protocol in slave mode.
Some Advantage of RS485 interface are: Providing the feature of RS 485 digital serial interface is advantageous, since the number of wires coming from the various sensors can be avoided and instead, only two wires can be used to interface multiple such PTX-3000 on serial port. For example, for a large heating system incorporating 16 thermocouples, under conventional method 16 dual core compensating cables will run from the heating system to the control panel, where as in case of RS485 interface, only two wires will run from the system to the control panel. Another advantage of RS485 interface is that, when to be interfaced with PLC – the additional analogue module is not required, since most PLC accepts RS485 interface on MODBUS RTU protocol.