Remote Terminal Unit (RTU)

DFA Remote Terminal Unit - Utility Grade

The DFA Remote Terminal Unit (RTU) is an open architecture non-proprietary unit, programmable, configurable and capable of Human Voice Interface. When located at a remote site, the RTU equipped with communications equipment serves as an monitor and control interface between on-site instruments, pumps, I/O devices, etc. and a System Control Computer (SCC) tasked with monitor and control software and communications drivers.

The System Control Computer (SCC) features a Microsoft Windows® operating system and DFA Monitor and Control software developed using National Instruments LabVIEW®, a leading industry standard process control language.

The RTU manufactured by DFA can be powered from several sources including solar power and is easily networked by phone, cellular, radio, RS 232 cable, RS 422 / IEEE 485, fiber-optic links or internet.

The DFA microprocessor based RTU has a unique 16 bid address which allows over 60,000 unit addresses per system and can monitor and control remote site status and functions, as well as serve as an Area Controller for other sites. Each unit is capable of peer to peer communication or transferring messages to and from other RTUs in the system by using an open communications protocol called OpenLINK™. The 'store and forward' capability of OpenLINK™ makes each DFA RTU a Repeater. Units can accept and execute commands from the System Control Computer (SCC) or another Area Control Remote Terminal Unit (A-RTU).

For reliability, each utility grade RTU has a battery backup system designed in for continued operation during power outages for up to 2 days. Both inputs and outputs are protected against surges and spikes. The RTU inputs are configurable and the RTU calls into the System Control Computer or base station on input value changes or at set time periods.

Each RTU is designed, manufactured and assembled in Hueytown, Alabama, a suburb of Birmingham, in accordance with the customer's specifications in a UL508A certified shop.

DFA offers several methods of interfacing with the Remote Terminal Unit (RTU).

DFA Monitor and Control software located on the System Control Computer (SCC) running a Microsoft Windows Operating System.
Remote access software such as Symantec PC Anywhere provides access to the SCC and operability of the DFA Monitor and Control software from a remote location such as home by using another computer or laptop, modems and remote access software. This provides the operator with a screen image that duplicates the base station.
When the Telemetry Monitor and Control System is equipped with an optional Dialer card and software interface, each RTU can be accessed using a telephone with a Touch-Tone keypad.

RTU inputs may be digital, analog, counter (16 or 32 bit), or Position Encoder. Input signal requirements are:

Digital or Counter - dry contact / 120v AC - DC / 24v AC / 12v DC
Analog - 4-20mA sinking / 0-5vdc
Encoder - 2 channel quadrature with Index and Home

RTU outputs may be digital or analog. Output signals provide:

Digital - dry contact (1A @ 120v AC - DC)
Analog - 4-20mA (Sourcing or sinking) or 0-5v DC

The DFA Remote Terminal Unit has an 8-bit or 10-bit data resolution for analog values and a 16-bit or 32-bit data resolution for counter values. Counters may also be programmatically set to any data resolution within the range of 16-bit to 32-bit.

Many types of RTUs are available: Expandable, Midi, Mini, Area, PLC and Custom.

Expandable RTU (E-RTU) utilizes a card cage design allowing any combination of inputs / output cards required by the customer's installation.

Group 1 E-RTUs have five I/O card slots available in the card cage.
Group 2 E-RTUs have 12 I/O card slots available in the card cage.
Program space is 32k SRAM / 32k EPROM / RTC.
System examples: process control, multi pump station, lift station, irrigation control, custom application .....

Midi-RTU (D-RTU) has a fixed I/O set, expandable.

8 Digital Inputs. 120vAC / 24vAC / 12vDC through a Relay Input printed circuit board.
4 Counter Inputs. Dry contact to DC power.
8 Analog Inputs. 4-20mA sinking, may be jumpered as digital inputs.
8 Relay Drives through a relay output printed circuit board.
1 Analog Output. (4-20mA / 0-5v)
Program space is 32k SRAM / 32k EPROM / RTC.
System examples: lift station, multi pump station, process control, irrigation control, etc.

Mini-RTU (M-RTU) is physically smaller and has a fixed I/O set.

4 Digital Inputs. &120vAC / 24vAC / 12vDC through a Relay I/O printed circuit board.
2 Counter Inputs. Dry contact to DC power.
4 Analog Inputs. 4-20mA sinking, may be adapted as digital inputs.
4 Digital Outputs. Dry contract through a relay I/O printed circuit board.
1 Analog Output. (0-5v)
Program space is 2k SRAM / 8k OTP-ROM.
May be solar powered.
System examples: tank level, remote valve, etc.

Repeater Unit - is used to relay the messages outbound and inbound on each 'Radial' leg. Up to 16 Repeater Units may be on each Radial leg with up to 8 Radials possible - star burst pattern. Up to 250 RTUs may be serviced directly by each RTU. A RTU may be AC or DC powered. Solar powering is possible if traffic flow is low. Two Repeater types exist: Store and Forward and Dual Frequency. For systems utilizing dual frequency repeaters, (two radios), a Repeater Board (P/N 0592) may be added to a Remote Telemetry Unit making it a combined RTU-Repeater.

Custom RTU - a whole range of custom RTU designs are under development or on the shelf. Consult the DFA manufacturing center for detailed information.

Programmable Logic Controller RTU (PLC-RTU) are protocol converters, translating PLC information to DFA data packets for SCC use. Check with the DFA manufacturing center for the currently supported protocols.

System options available include:

Master / slave control shift via Data Modem or radio.
Remote monitoring and after hours control via Auto Answer Data modem.
Voice reporting over the phone system or voice radio channel.
Remote system control (limited) via Touch-Tone™ phonepad.

Types of RTU Enclosures available:

NEMA 12 epoxy painted steel.
NEMA 4 epoxy painted steel.
NEMA 4X fiberglass with interior RFI paint.
NEMA 4X stainless.

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