For integration into the automated process control systems, the Irga-2 computer uses the RS-232 connector. The computer can be connected to the ICS devices either directly through this connector or through matching adapters: The AV-2 output signal generating unit, the АS-485 adapter, or the USB adapter.
The connection method should be selected taking into account:
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type of used automatic process control devices
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terms of use
It is possible to connect the following types of devices to process control systems:
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Analog devices with a unified input current signal of 0-5 mA, 0-20 mA or 4-20 mA (the AV-2 adapter is used)
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Devices with a discrete input signal - frequency signal 0-1000 Hz, amplitude 12-24 V (the AV-2 adapter is used)
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Devices with RS-232 interface (two AS-485 adapters or direct connection to the RS-232 connector of the computer), a modem can be used as a data transmission device
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Devices with RS-485 interface (the AS-485 adapter is used) (point-to-point connection)
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Devices with RS-485 interface (the AS-485 adapter is used) (network connection)
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Devices with the RS-485 interface using the Modbus RTU network protocol (the AS-485 adapter is used)
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Devices with Bluetooth or WiFi adapters (the USB adapter is used)
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Devices with an Ethernet interface via an RS-232/485 Ethernet converter (when using devices with an RS-485 interface, the AS-485 adapter is used)
The flow charts of all available connection methods is shown in Fig. 1-8.
Fig. 1. Unified current circuit
The AV-2 adapter is used in the circuit, which is connected to the computer with a standard RS-232 interface cable. The range of the output current signal of the AV-2 adapter can be 0-5 mA, 0-20 mA or 4-20 mA (determined when ordering the AV-2 adapter). The magnitude of the signal is proportional to the instantaneous flow rate of the medium being measured. The adapter signal is active, i.e. cannot be used in a two-wire switching circuit.
Fig. 2. Discrete signal circuit
The circuit uses the AV-2 adapter, connected to the computer with a standard RS-232 interface cable. The output frequency signal is a pulse with a frequency of 0-1000 Hz, an amplitude of 12 to 24 V. The pulse repetition rate is proportional to the instantaneous flow rate of the measured medium, the unified frequency range (0-1000 Hz) can be changed when ordering the adapter.
Fig. 3. AV-3 output signal
The communication protocol enables continuous monitoring all instantaneous parameters of the medium (flow rate, temperature, pressure, etc.), emergency situations in real time.
The controllers are used as a HART slave device (Rev. 5) for reading the flow rate of the measured medium and diagnostics by HART masters. Burst HART mode is not supported.
This scheme can be used in automated systems for accounting and control of energy and energy resources, taking into account the thermal and hydraulic heat supply and heat consumption systems in technological processes.
Fig. 4. Scheme with RS-485 interface (point-to-point connection).
The AS-485 adapter is used in the circuit, connected to the computer with a standard RS-232 interface cable.
On the part of the process control system, a digital controller (or computer) with the RS-485 interface, or with the RS-232 interface and the second AS-485 adapter can be used.
The length of the RS-485 communication line is up to 1 km, the line is galvanically isolated in the AS-485 adapter and has a single power circuit (that is, the AS-485 adapters can operate from one power supply). Communication protocols and software correspond to the previous figure (Fig. 3).
Fig. 5. Scheme with RS-485 interface (network connection).
The AS-485 adapter is used in the circuit, connected to the computer with a standard RS-232 interface cable, the network protocol - Modbus RTU, is provided by the AS-485 adapter.
On the part of the process control system, a digital controller (or computer) with the RS-485 interface, or with the RS-232 interface and the second AS-485 adapter can be used.
The length of the RS-485 communication line depends on the transmission speed (1,200-115,200 bps), it can be more than 1 km, the line is galvanically isolated in the AS-485 adapter and has a single power circuit (i.e., all AS-485 adapters can work from one power supply unit).
The network may include up to 32 computers (with AS-485 adapters) and any other devices supporting Modbus RTU.
Fig. 6. Modbus network diagram using RS-485 interface.
The communication protocols are made according to the Modbus RTU specification, they are add-ons of the communication protocols via the RS-232 interface and are their functional counterparts. Protocols are also open to use.
Additionally, for monitoring instant parameters, there is an OLE server MBMonitor and an OPC server (specification DA 2.0) - MBOPC.
Fig. 7. Scheme with USB interface.
The USB adapter is used in the circuit, which is connected to the computer with a standard RS-232 interface cable.
The WiFi adapter is connected to the USB connector of the USB adapter (the Bluetooth adapter is used less due to its short range). On the part of the control system, a digital controller (or computer) with a USB interface and a WiFi adapter (Bluetooth) can be used.
Using a WiFi adapter allows connection of computers to a network based on Wi-Fi standards. The WiFi adapter operates at speeds of 1, 2, 5.5 and 11 Mbps, using automatic speed control to ensure optimal speed and reliability of the connection. These adapters provide communications from 100 m to several kilometers (when using an outdoor antenna).
Fig. 8. Scheme with COM port to Ethernet converter.
It allows the computer to directly integrate into the automatic process control system (driver/communication protocol required).
Advantages:
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possible simultaneous access to the same serial port from multiple devices via Ethernet
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indication of communication on serial ports and Ethernet
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communication between two devices with serial interfaces via Ethernet