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Chapter 1 - Introduction

Overview Specifications

Ordering Information

Available I/O Modules


I/O PLEXERs are a family of small, completely self-contained, industrial grade, remote data acquisition and control systems, which exchange data with a Host computer via a serial communication link. Controlled by a Host, I/O PLEXERs are located near the sensors and actuators. The serial link eliminates the need for expensive and noise prone field wiring between sensors and actuators, and a central control room.

In applications such as remote process monitoring, factory automation, and energy management, a variety of signals must be transmitted over long distances. Instead of requiring expensive, multi-conductor, sensor wiring for each signal, cabling costs can be reduced significantly by using I/O PLEXERs and a single communication circuit.

One of the most useful features of the I/O PLEXER is that in addition to gathering "raw" data, it can be instructed to perform many ranging and statistical operations upon that data before it is given to the host; thus allowing the host to spend less time manipulating numbers and more time gathering them. Also, the I/O PLEXER is able to spend more time exposed to the data which in turn allows it to base it's responses to the host on more samples of the data. The I/O PLEXER may also be directed to manipulate outputs in specific ways to produce delayed or repetitive effects.


Each I/O PLEXER Master unit will hold any mix of 16 analog or digital, electrically isolated input or output modules which can interface to a wide variety of sensors and actuators.

The I/O PLEXER Digital Expander, in an identical enclosure, provides an additional 16 digital I/O module positions for each Master unit. Up to three Digital Expanders can be attached to each Master chassis.

I/O PLEXER networks can service over 4000 analog and/or digital I/O lines in various combinations. 

Product Test:

Every I/O PLEXER is burned-in while operating in a network for a period of at least 24 hours at 70 C, prior to shipment.

Every analog I/O module is tested white its operating environment temperature is cycled over the specified operating range of 0 C to 60 C for a period of 24 hours. A computer record is maintained for every analog I/O module.


System response, or throughput for the I/O PLEXER can be calculated using appendix B.

I/O Signal Compatibility:

I/O PLEXERs use duTec I/O modules to match signal requirements exactly. With a direct interface to sensors, no external signal conditioning is required. Furthermore, all duTec modules feature total electrical isolation, but module-to-logic and module-to-module. Analog modules are able to measure:

A full range of industry standard digital modules is available for AC, DC, and dry contact inputs and outputs to hundreds of volts.

Thermocouple modules provide a cold reference junction compensation. I/O PLEXER instructions provide linearized thermocouple and RTD sensor data. Engineering unit conversions are handled at the Host level.

Built-in Diagnostics:

On power-up, the unit self-tests for system faults and reports via a sequential display. Should hardware or firmware fail, an on-board hardware watchdog provides safe shutdown by turning off all outputs. Normally ON modules are available for those loads that must remain ON.

Easy Setup:

The I/O PLEXER has its own power supply; no need to purchase or reserve space for an external supply. A push-button and on-board LED indicator configure unit address and baud rate. Removable terminal strips allow the attachment/removal of multiple cable sets in one step. This modularity greatly reduces troubleshooting and upgrade delays.

Protocol Compatibility:

The I/O PLEXER instruction set core complies 100% with the OPTO-22 OPTOMUX serial communication protocol for remote data acquisition and control. With this speak-only-when-spoken-to protocol, which only uses ASCII printing characters, a Host transmits inquiry requests to the I/O PLEXER to determine the status of its various process inputs. Based on the reported status, the Host makes control decisions and transmits this data, as instruction messages, to the I/O PLEXER  which uses the new decisions to make the proper changes to its various actuators. Both the Host and the communication link are essential elements in this data acquisition and process control scheme.

Originally, the protocol only allowed for all analog or all digital I/O chassis. Depending on application requirements, each I/O PLEXER can respond to up to five different function addresses. With their abbreviations they are:







Master Unit Control function address

Master Unit Digital I/O function address

Master Unit Analog I/O function address

1st Expander Digital I/O functions address

2nd Expander Digital I/O functions address

3rd Expander Digital I/O functions address

It is this multiple function addressing capability of I/O PLEXERs that allows them to utilize, without modification, software developed for competitive products. Similarly, I/O PLEXERs can operate simultaneously on the same network with these products.

Available I/O Functionality:

Analog Inputs

Input Value Determines signal levels, with 12 bits (One part in 4095) resolution
Offsets Input values can be software offset, with 12 bits resolution, over the module's specified range.
Gain/Slope The amplitude of input values can be software multiplied by factors ranging from 0.25 to 4.0.
Range Limits The occurrence of input values falling out of user defined upper or lower limits can be flagged.
Minimums The minimum level of input values can be captured.
Maximums The maximum level of input values can be captured.
Averages Can calculate average input amplitude for 1-65,535 samples.
Temperature Can linearize in, C, inputs from the thermocouples and RTD's. Will also return temperature probe data.

Analog Outputs

Level Value Can set Output levels, as a fraction of the module's full scale range, and are specified with 12 bits resolution.
Waveforms Analog outputs can provide square, triangular, sawtooth or ramp Waveforms. Maximum and minimum amplitudes, as a fraction of the output module's full scale range, are specified with 12 bits resolution. Waveform periods are specified from 0.1 to 6,553 Sec made up of at least 10 segments.

Digital Inputs

Read Read the ON or OFF state of all inputs.
Pulse Widths The duration of a single pulse or total On/Off time of consecutive pulses can be resolved to the nearest 0.01 seconds for a max total of 10.9 Min, or 46.6 Hrs with multiplied resolution. Positive or negative edges initiate measurements. The time scale can be multiplied by a factor of 1-256 on a system wide basis.
Pulse Counting Pulses can be counted up to a total of 65,535. To be reliably counted, pulses must have mini minimum OFF times of 1 msec. Thus the maximum counting rate for a 50% duty cycle squarewave with equal ON and OFF times for a total of 2 msec would be 500 HZ.
Edge Detection OFF-to-ON and ON-to-OFF transitions can be detected within 1 msec of their occurrence. Action is only reported each 10 msec.
Note: The response time performance of digital input instructions can be limited by the delay in the input modules themselves which can have ON plus OFF delays of up to 40 msec.

Digital Outputs

Set Outputs Can set individual or multiple outs ON or OFF.
One Shot Can generate ON or OFF pulse durations of up to 655.35 seconds with a resolution of 0.01 seconds. Resolution can be further multiplied by a factor of 1-256 on a system wide basis. Re-triggering is available.
Delayed Can generate delayed ON or OFF outputs of up to 655.35 seconds with a resolution of 0.01 seconds. Resolution can be further multiplied by a factor of 1-256 on a sysetm wide basis.
Squarewave Can generate squarewaves with programmable ON and OFF periods. ON and OFF periods have a base range from 0.01 to 2.56 seconds. Resolution can be further multiplied by a factor of 1-256 on a system wide basis. Re-triggering is available.
Pulse Generator Can generate 1 to 65,535, 50% duty cycle pulses whose equal ON and OFF periods can range from 0.01 to 2.55 Sec. Resolution can be further multiplied by a factor of 1-256 on a system wide basis.

Extended Capabilities:

In addition to operating under the control of a Host, the I/O PLEXER has the ability to perfoorm Local Control Functions without the Host. Local Control Functions (LCFs) can insure the continued safe operation of closed loop control should the Host or its communication link fail. In addition, LCFs can substantially reduce Host computational load or communication traffic.

Once characterized, Local Control Function Blocks enable the I/O PLEXER to perform control tasks without the constant involvement of a Host computer. After configuration and activation via Host instructions, LCFs take data from their input ports, computations and send the results to their outputs, where they may drive output modules, or other  I/O PLEXER internal functions.

Utilizing the LCFs to perform simple logic tasks such as analog comparisons, summations, differences, sequence generating or state machine operations, eliminates the need for programmable controllers or special purpose circuitry. This capability allows a more effective use of the Host computer, and its' communication link, because the LCFs handle the operation of the designated control function. In the meantime the Host is only required to monitor over-all system status and generate the system displays and reports. This is particularly valuable for systems using modems for communication.

Communication Watchdogs:

The I/O PLEXER can be instructed to implement alarm and fail-safe states in the event of a failure.


Network Communication:

duTec supports several standards for transmitting serialized I/O data between the Host computer and the I/O PLEXERs. In addition to hard-wiring, Built-in modem control lines allow the use of telephone, fiber optic, and radio modems at baud rates to 38,400.

Maximum Distance
Serial Link















In addition to network communications, a separate local RS-232 port, with the same Baud rate capabilities, provides the means for Host communication with local serial devices such as keypads, printers or displays. Actual interaction with these devices is controlled via the Host computer in the form of character strings embedded in standard protocol instructions.

It is not possible to directly access the analog and digital I/O data from the local RS-232 port; however, this data can be obtained by the Host computer and relayed to the auxiliary device connected to the Local RS-232 port. Device pinout for this port can be found on the cover plate. Data format is 8-databits, 1-stopbit, and no parity.

Physical Characteristics:

Power Standard 90 - 264 Vac @ 30W (47-440 Hz)
Option /B 9 - 18 Vdc @ 33W
Option /C 18 - 36 Vdc @ 33W
Environment Temperature 0 - 60 C
Humidity 95% non-condensing
Package Type Stainless Steel
Length 17.25 in. (44 cm)
Width 5.0 in. (12.7 cm)
Height (w/modules) 3.5 in. (8.9 cm)
Weight 4 lbs. (1.8 kg)
Options /3+ Expansion ports for up to 3 Digital Expanders

Ordering Information

Specify duTec products by model number, e.g.,
IOP-AD I/O PLEXER for Analog and Digital Signals
IOP-D I/O PLEXER for Digital Signals Only
IOP-DE Digital Expander chassis (Master chassis must have /3+ option)

Options are specified by a series of suffixes to the model number, preceded by a slash. For example:
IOP-AD/3+ Allows the use of up to three Digital Expanders on an analog capable I/O PLEXER.
IOP-D/B Specifies a digital only I/O PLEXER with a 12Vdc compatible power supply.

Available I/O Modules

See our Module Data Sheet for complete listing of available modules, as well as specifications.

6979 Wales Road
Northwood, OH 43619
800-248-1632 Phone
419-666-4700 Phone
419-666-4702 Fax

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