I/O & Terminal Blocks (Part 1 of 3)

Sept. 9, 2003

Compatibility counts

On the surface, I/O selection looks like it should be an easy process. Determine your specific needs and, if the voltage numbers match, field equipment and I/O systems will work together, right?

Circuit compatibility is not guaranteed among all manufacturers' I/O systems and all field equipment. For multivendor environments, the IEC has established value ranges for interoperability of several electrical parameters. Even so, end users may want to use the same supplier for sensor and I/O products whenever possible.

Because of the huge vendor response to our query, the following is the first of three installments on the subject of I/O and terminal blocks. The next two will be published the weeks of September 15 and 22.

Intrinsically Safe

FieldBarrier combines the functions of a short circuit-protected junction box with an intrinsic safety barrier, making it suitable for use in Class I, Div. 2 or Zone 1. The field-mountable, four-channel device interfaces with 16 intrinsically safe field instruments. Each channel supplies 40 mA of current to the field devices while spurs can be as long as 394 ft. It has short circuit and overload protection, galvanic isolation, and operates in temperatures to 185° F.


330/486-0002 www.fieldconnex

Hazardous Terminals

The Bus Terminal line is approved for use in Class I Div. 2, Class II Div. 2, and Class III areas specified by UL1604 and the NEC code. Terminals are available in one, two, four, and eight-point modules in a very slim housing. The terminals snap together on a standard DIN rail and can connect to networks, including Ethernet, Profibus, ControlNet, and DeviceNet.

Beckhoff Automation

952/808-6502 www.beckhoff.com

Signal Conditioners

Compact, plug-in Juxta VJ signal conditioners include a universal temperature converter, isolator, and a distributor. Its universal power supply allows the unit to run on both AC and DC voltages from 100-240 V (50/60 Hz) and 15-30 VDC. A hand-held terminal or PC allows a full range of inputs and outputs to be selected at the work site. It has an analog output and Modbus, ASCII, Modbus RTU, and PC-Link communications.


800/258-2552 www.us.yokogawa.com

Configurable Signal Conditioner

The DSCP81 isolated voltage/current input signal conditioner protects measurement and control signals from effects of noise, transient power surges, internal ground loops, and other hazards present in industrial environments. It measures voltages up to 1,000 VDC or currents up to 100 mA, and its output signal provides voltages up to 10 VDC or currents up to 20 mA. The input/output type, measurement range, and alarm relay output are software-configurable.


800/444-7644 www.dataforth.com

New Generation of Distributed I/O

Adam-8000 is a new distributed control I/O system that extends the vendor's Adam family into critical control applications. This series adds determinism to meet reliability requirements. Its modular design can be configured as a control system by selecting a preferred CPU, communication interface, and various I/O modules. It includes support for all popular fieldbuses.


877/294-8989 www.advantech.com

Analog I/O Has HART

Eight-channel analog I/O modules with the HART protocol work with Allen-Bradley's ControlLogix and Honeywell's Experion PKS. Each module also acts as a HART master, allowing communication with HART field devices. When used with an asset management system, the I/O modules provide configuration, calibration, diagnosis and troubleshooting of smart field devices from a desktop PC. Setup is easy with support from programming software.

Spectrum Controls

425/746-9481 www.spectrumcontrols.com

Mostly Controllers

MOST controllers are now available with Woodhead's RJ-Lnxx product line, including IP-67 sealed RJ-45 receptacles and plugs, harsh-duty patch cords, and industrialized Ethernet switches. The controllers are rugged, field-mountable platforms intended for process applications that might have previously used PLCs. They work with MTL8000 process I/O components, are programmed in IEC 61131-3 languages, and have redundant Ethernet communications ports.

MTL Open System Technologies

800/835-7075 www.mtl-most.com

Ethernet I/O

Model 2500 intelligent I/O system with Ethernet provides remote I/O for PLCs, HMIs, or the company's model T800 visual control system. Options include Modbus, DeviceNet, and Profibus protocols. The I/O system has analog and digital inputs and outputs for all standard signal types. Sensors such as thermocouples, RTDs, and strain gauges can be direct-wired to inputs. Custom linearization can be done for special transducer curve fitting.

Eurotherm Invensys

703/669-1355 www.eurotherm.com

Optical Isolator

For use with incremental quadrature encoders, isolation circuitry in this optical isolator module eliminates ground loops, reduces signal degradation from long cable runs, and can distribute an encoder signal to multiple input devices. This provides a better interface for control systems that are marginal due to poor signal compatibility with the receiving electronics, or installations that are particularly susceptible to noise or grounding problems.

BEI Technologies

800/350-2727 www.beiied.com

PC/104 I/O Module

The AIO-104+8 provides eight single-ended 12-bit inputs, two 12-bit D/A output channels, and 16 TTL digital I/O in a PC/104 module. A/D inputs are software-selectable/ for 0-5 V, 0-10 V, +/-5 V, and +/-10 V ranges and can be configured via hardware for measuring a 4-20 mA current loop. The inputs have 5 MHz bandwidth track/hold and 100 Kbps throughput rate. The two 12-bit D/A channels are jumper selectable for 4.095 V or 2.048 V full-scale. Price: $299.

Sealevel Systems

864/843-4343 www.sealevel.com.

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