Modbus I/O for 12 VDC Powered Systems


The SCADALink RIO100 Modbus I/O Controller and Analog I/O Expansion Modules can be used to provide stable high resolution I/O expansion for smaller RTU and Controller equipment and for control system operating on 12 VDC power systems.

I/O Expansion for Small RTU and Flow Computer Systems

Existing small RTU and EFM systems often do not have adequate integral I/O and sometimes require additional I/O expansion. The SCADAlink RIO100 Modbus I/O Controller can be used with I/O expansion modules to expand these RTU or EFM system I/O with up to 64 additional I/O points. Modular I/O Expansion include 4 Point 4-20ma Input (AI4), 4 Point Digital Input (DI8), 8 Point Digital Output (DO8), 4 Point 4-20ma Analog Output (AO4); and Combo I/O (1 AI, 1 AO, 2 DI, 2 DO).

A common application for Modbus I/O expansion to add casing and tubing pressure measurements to a EFM system on a gas production well.

The RIO100 system can be connected to RTU/EFM systems via RS232 or RS485 connections.

24 VDC Loop Power for 12VDC Powered Systems

The SCADALink AI4 and COMBO-I/O I/O Expansion Modules have integral 24VDC DC to DC Converters that generate 24 VDC Loop Power from a 10-30 VDC Supply Voltage. This allows provides stable 24VDC loop power for 4-20ma instrumentation operating on 12 VDC systems.  Frequently analog input channels do not operate reliably on 12 VDC power systems due to noisy power supply or inadequate 4-20ma loop voltage.

Isolated 4-20ma Inputs

SCADALink RIO100 Modbus I/O Expansion can be useful in applications where grounding issues can cause inaccurate or problematic analog input channels for PLC/RTU Controller with no-isolated analog inputs.



Wireless Pump Control for Small Water Systems

Remote Wireless Pump Control is a pervasive requirement in many industries.

A common Remote Pump Control application is to control pump operation based on a remote tank level. Pump(s) are started and stopped or the pump rate controlled to maintain a level in an elevated tank or reservoir. High and low level switches or level transmitters are used at the tanks to monitor the level for control and alarming.

Dedicated and Lease Line Replacement for Remote Pump Control

Where the tank and reservoir is close to the tank, level switches or level transmitter were hardwired to the pump control panel using dedicated cable. Over time, the dedicated cable may become damaged becoming difficult or costly to repair.

In other instances where the tank and reservoir are located a farther distance from the tank,  leased telephone lines were used.  Lease telco line can become damaged;  obsoleted by the telco or become overpriced.

In both these instances, wireless technology is viewed as replacement alternative. Technologies that can be used including Wireless I/O Telemetry, SCADA, and Wireless IoT.

Wireless I/O for Small Water Systems

It has been our experience that for Small Water Systems, Wireless I/O Telemetry is by far the most cost effective and easiest technology to deploy and maintain for Remote Pump Control in Small Water Systems. This is especially the case for Dedicate or Lease Line Replacement for existing Elevated Tank or Reservoirs since there is minimum number of signals required to be transmitted. It could range from 1 (Analog Tank Level) to 6 (Hi Level Switch, Low Level Switch, Hi-High Level, Intrusion, & Analog Tank Level) signals.

Wireless I/O Telemetry is the replacement of existing wired signals with Wireless Technology to mirror the I/O signals –  be it Digital Contacts or 4-20 ma Analog Signals.  With use of  Wirelesss I/O Replication Technology, no other part of an existing Control system needs to be changed.  The existing pump control panel can be retained. Hardware relay logic can be kept. This can be important for Small Water System applications where towns or villages may not have the personnel to deploy and maintain systems that require specialized programming or IT knowledge if PLC, HMI, or SCADA Systems are deployed.

Even in new Pump Control applications, Wireless I/O approach may be the most simple and most reliable solution for transmitting tank level signals.

SCADALink Wireless I/O Replacement Solutions are preconfigured and operational out of the box without configuration.  In the case where the remote tank location has no line power,  SCADALink Solar Powered Wireless I/O packages are available.





Remote Generator Monitoring and Control

Mobile Diesel Backup Generator for Office Building

Gas, Diesel, Natural Gas, and Propane Generators are seeing more pervasive use to provide emergency AC power during weather, fire, and flood emergencies.

Emergency Backup AC Power

Emergency Backup AC power is needed to provide backup power for critical AC loads at homes, offices, businesses, plants or telecommunication sites when grid AC power is lost due to weather emergencies.

Mobile AC Power

Mobile and Portable Generators may be deployed to power temporay equipment such as Pumps, and Lights.

Remote Monitoring and Control

For both Backup and Portable Generator applications, there is need for Remote Monitoring and Control.

Remote Monitoring is required to insure that backup power system is ready and available in case of emergency. Alarm Notification is required to alert personnel when an Generator is energized or has failed or is low on fuel.

Generator can be remotely control at remote unattended sites.

Remote could be as short distances as 100′ from a generator skid to the nearest electrical room for a plant or business. In these situations a Wireless I/O remote control solution could be utilized to monitor and control the generator versus running addition control wiring.

Alternately the Remote Monitoring and Control could be halfway across the continent and state for large Enterprise operations such a Telecom Company or Pipeline Company. In these situations, SatSCADA can be deployed.


PSC-24 Provides Stable 24VDC Control Power for Mobile Equipment

PSC 24 12 to 24vdc dinThe SCADALink PSC-24 DC to DC Converter is frequently used as a power conditioner to power PLC and Controllers used Mobile Equipment such as Pumps & Generators.

Mobile Equipment typically utilize 12/24 VDC Battery Systems charged by an alternator. PLC and Controller Equipment typically run directly off the 12/24VDC power system.

PLC and Controllers systems can be affected by voltage droops caused by cranking or by noisy DC power from alternator systems.

Voltage droops can cause PLC/controllers to restart or halt causing Pump or Generator shutdowns. Voltage droops can cause low supply voltage on 4-20ma Loops causing improper I/O readings causing improper control operation including shutdowns, unstable control, and incorrect process setpoints.

Noisy DC Power can often cause unstable, erratic, and noisy Analog Input Channels.

In addition, many PLC, Controllers, and Instruments are designed to run on 24 VDC Power and cannot operate or operate unreliably on 12 VDC power sources.  The PSC-24 can be used to provide stable 24VDC power from existing 12 to 24 VDC Battery Systems on Mobile Equipment.


Remote Industrial Video Surveillance

The rapid increasing use of Camera Technology in all aspects of personal, commercial, and industrial technology has made this technology smaller, cheaper,  more powerful, and more rugged.  This also leads to increase opportunity for industrial use.

Cameras are another form of sensor that can be monitored automatically or manually by a user. Use of Onboard and Remote Video Analytics can automatically derive sensor readings.  User viewing of image or video can be used for remote reading of manual gauges or gauge boards, and for remote site patrol.








Video Analytics for Automatic Sensor Reading

Video Analytics or Image Analysis technologies can be used for Automatic Sensor Readings.  For example:

  • Temperature can be read using Thermal Cameras
  • Remote Gauges can be read by Image Analysis on Dial Position or Character Recognition
  • Object Detection can be used to detect Presence and Position of Equipment, Process Condition, or Levels.
  • AI Image Analysis techniques can be used to Classify Objects for sorting or recognition applications.

Remote Reading of Manual Gauges

The ability to view image and videos remotely can used to remote read manual Gauges. This can be a cost effective alternative upgrade to electronic instrumentation in legacy plant operations with mechanical and pneumatic instrumentation where upgrade to electronic instrumentation is too expensive. In critical applications such a flood warning  remote image and live stream views can augment sensor based monitoring.


Remote Site Patrols

The use of video cameras in a remote monitoring or SCADA system can augment or even reduce the frequency for onsite visits.   Remote image views of sites can help ensure higher levels of environmental and safety compliance.

SatSCADA for Remote Industrial Video Surveillance

SatSCADA integrates both traditional sensor monitoring and video monitoring in a powerful simple to use platform. Capture and transmission of still and video imagery is supported by SatSCADA. SatSCADA supporting radio, satellite, and cellular technologies ensures connectivity in the most remote locations.

Video Surveillance Integration in PumpMate

Video Surveillance is now supported in our SCADALink PumpMate for water transfer automation.  Video monitoring can help assist in operations monitoring and  worker safety.

I/O Mirroring vs RTU Polling in Wireless Automation Systems


The following techniques:

  • I/O Mirroring
  • RTU Polling

are used in wireless automation systems.

“I/O Mirroring” aka “I/O Telemetry” is the technology where Analog Signals (4-20ma) and Digital (Contacts) Process Signals are replicated from a transmitter to receiver end by wired or wireless means.  RTU Polling is technique where a master station polls remote stations via a protocol such as Modbus.

I/O Mirroring is best suited for applications when there is a small number I/O points to replicate.  I/O Mirroring is used to replace a broken or failing wire in existing or legacy systems; or as an alternatively to cable. I/O Mirroring is used when there is no facility in the PLC or RTU for polling. There may not even be a RTU or PLC in a hardwired control system.  In this case, I/O Mirror is the only option.

I/O Mirroring is best deployed when the operation or company has limited internal PLC programming support staff. For example in towns or villages with small water systems, it is often better to use I/O Mirroring techniques.

RTU Polling is used when the application or operation has many sites, as in large Oil and Gas SCADA systems, or large water systems and they have Automation Staff familiar with PLC / SCADA Programming.  RTU Polling allows the minimization of I/O hardware and wiring at the master site.

With both techniques, appropriate error handling is to be understood for communications failure and for system startup. With I/O Mirroring one must look at use of I/O Fail States, or the use of a Communications Fail Signal. Similarly in use of RTU Polling approach the PLC programming logic must appropriately handle communications failures,  retries, and setting default register values in event of communication failure.

SCADALink RIO900 supports both techniques.


Satellite Communications for River Intake Pump Station Monitoring & Control

Water Intake Pump Station Monitoring

River Intakes pose SCADA Communication Challenge

River Intake Pump Stations are commonly located along river banks where it can prove challenging to find reliable wireless communication solutions whether being private radio systems or cellular based.   Intake locations often will have radio frequency (RF) obstructions by terrain and/or foliage which make terrestrial RF communications unreliable or near impossible.  Repeater systems are often deployed for terrestrial wireless communications systems. Even with repeater system, SCADA communication are still frequently unreliable.

Given the connectivity obstacles, satellite data communications can be a good alternative. Satellite systems can be (GEO) Geosynchronous Earth Orbit or (LEO) Low Earth Orbit based satellite networks.

Satellite solutions can range from high speed VSAT (GEO) solutions to lower speed packet data services such as Iridium SBD Short Burst Data  (LEO) & Inmarsat IsatData Pro (GEO).

For many applications, these low speed satellite communications can be a better alternative to unreliable terrestrial communications. A benefit of the low speed satellite communications solutions is that they utilize small omni-directional antennae that make these systems easy to deploy and do not require installation by satellite communications technicians.

The utility of satellite communications can be applicable both to permanent or temporary water intake station sites.

Solve Long Standing Unreliable SCADA Communications

Satellite connectivity can be a good alternative for replacement of  troublesome unreliable terrestrial SCADA communications.  Over the years , unreliable terrestrial SCADA communications at intake stations have been a common problem in municipal and industrial systems. Existing deployments  of intake stations SCADA communications are often unreliable. The difficulty and high cost of rectifying these shortcoming prevented proper resolution.  We have seen this in water systems at towns and cities; oil and gas plants; mines, and manufacturing plants. Now, satellite connectivity can allow cost effective and timely resolutions of these long standing and effective resolution of these communications problems.

Monitor Temporary Water Sourcing and Pumping Applications

Satellite communications can be a particularly good alternative for temporary water pumping applications since many of these sites are deployed in remote areas with limited cellular coverage.  Satellite connectivity can ensure connectivity for temporary water pumping applications. Critical parameters such as river and lake levels, flow,  pump RPM , and pump run can be monitored or controlled.

Emergency SCADA Communication

Satellite communications can be a particularly good alternative in emergency monitoring. Forest fire or flood  emergencies can adversely affecting the integrity of water supply system requiring additional monitoring of water quality.

SCADALink Satellite Communications Solutions

Bentek Systems supports both LEO and GEO based satellite connectivity solutions.

The SCADALink SAT50 uses Low Earth Orbit (LEO) satellite technology which ensures connectivity at virtually anywhere. It does have attendant latency (60 seconds +), low bandwidth and higher data costs. This solution may be useful where the site is located where there is no view of GEO satellite.  This could be sites a very northerly elevations where there is extremely low elevation angles to GEO satellites or in very rugged terrain that there will be line of site obstruction by trees, river banks, hills, or mountains. SAT50 based systems are ideal for sites that require less frequent updates (hourly).

If there is clear line of site to a GEO satellite, our  SAT100, SAT110 and SAT140 that use GEO satellite technology is a another alternative. It  will provide reliable connectivity to site with high latency, low bandwidth with more cost effective data costs. This solution would be suitable for applications that requires updates down to 5-10 minute intervals.

In recent years, the importance of adding real-time data and alarm call outs to Water Intake Pump Station Monitoring have become more prevalent.  It helps improve the overall safety and adds another level of protection for environmental concerns. Additionally, having real-time monitoring can reduce the need for and the number of onsite staff; and reduced site visits while maintaining safety.


Benefits of Managed Cellular Data Services

The ubiquity of cellular communications has enabled simple and reliable data connectivity via cellular networks for SCADA applications. There are many benefits to using a managed cellular data communications service company.

Initially, systems were deployed using public Static IP. With increasing security threats such as Denial of Service (DOS) attacks,  Malware, Virus and other Hacking;  public static IP addresses are no longer acceptable.  This creates the importance of deployments with private APN / Private IP.  Depending on Carriers or geographical areas private IP/APN or static IP can be unavailable to non Enterprise Accounts or require longer contracts.

Frequently organizations do not have dedicated in-house technical support for Cellular Data Communication Networks or they have high staff turn-to maintain in-house support for data network support. In order to successfully manage ones cellular data a company would be a variety of highly skilled staff.

SCADALink provides Extended Managed Cellular Data Services for SME’s, Industrial, and Municipal Clients.  SCADALink Managed Cellular Services include:

  • Security –  Private APN and VPN SetupCommunication Services Management
  • Network Monitoring – Alerts for Outages, and Excessive Data Usage
  • Multi-Carrier Options
  • Roaming
  • Activation
  • Cellular Path Studies & Coverage Verification
  • Equipment and Application Technical Support
  • Redundancy and Fail-Over to Private Radio, Fiber, Satellite, Dual Cellular Carriers
  • Equipment Supply
  • Troubleshooting
  • Airtime Cost Optimization

Applications where Managed Cellular Data Services are beneficial

The following applications are where managed data services are beneficial.

  • Video Surveillance Systems – Mitigate Potential Excessive Airtime Usage
    and Overage Costs
  • Control System Networks –  Mitigate OT and IT Security Threats
  • Mobile Applications –  Availability and North American Roaming 24/7

SCADAlink is a leading provider in SCADA communication technologies. With over 20 years of experience in providing industrial remote monitoring-and-control solutions that range from the Oil & Gas to Water industry, our experience in the field ensures that customer expectations are met with reliable products and quality services.You can count on us to manage your cellular data communications.

Read more on SCADAlink’s services here

Modbus Communication with the SAT50 Iridium Satellite Modem


Satellite Communication technology is commonly utilized for remote site communications when there is no other practical means available such as when the site is located in areas not serviced by terrestrial communications such as dedicated line, or cellular. The site may be located in rugged terrain where line of site communication to a radio or cellular tower can obstructed by trees, hills, and mountains. Alternatively the application may be mobile so that an elevated antenna tower cannot be deployed.

GEO vs LEO Satellite Communication Technology

Satellite communications can use either Geostationary (GEO) or Low-Earth Orbit (LEO) satellite technology.

GEO satellite systems (such as VSAT or Inmarsat) utilize Geostationary satellites located at a fixed location approximately 23,199 miles above the equator to relay data from a ground station to satellite data terminals.  The Geostationary remains fixed relative the ground station and remote data terminals; a GEO satellite terminal located at a fixed site will have the same constant view to the Geostationary satellite at all times. Remote sites located at extreme northerly or southerly latitudes will have a extremely low look angle (ie 4 degrees in Fairbanks Alaska) to the GEO satellite and thus can be easily obstructed and be unreliable.

LEO satellite systems such as Iridium or GlobalStar use a network of Low Earth Orbit Satellites (66 satellites for Iridium) orbiting at a lower altitude above the earth (483 miles for Iridium constellation).  The motion of the Iridium satellite network over the site insures a only a short period where there is no view to one of the satellites. The low altitude of LEO satellite systems provide low latency path for voice and data communications but at a higher data costs. The Iridium network includes SBD (short burst data) packet data mode that is designed for M2M, GPS tracking, and messaging applications.

High Availability Low Bandwidth Communications Applications

The SCADALink SAT50 Satellite Modem operating on the Iridium SBD network is designed for SCADA communications to remote M2M applications where cost effective but reliable low bandwidth communication is required.  This can be ideal for some remote monitoring, data retrieval  applications, or remote control applications.

The SAT50 is easy to deploy and cost effective since no large towers are required to clear obstructions.  As long as the SAT50 can see a reasonable degree of the sky, the SAT50 will communicate. Even within heavily treed areas there should be clear sky overhead. This makes the SAT50 ideal for mobile and temporary applications where the site location cannot be widely cleared of trees and foilage. As an example, pipeline applications where equipment is installed on pipeline right of ways may not have clearance from obstruction from foilage.

Modbus Protocol over the Iridium Low-Earth Orbit Satellite Network

Modbus is a REQUEST – RESPONSE Master – Slave protocol commonly used in SCADA Communications over Wireless networks.  Modbus Protocol (Modbus RTU, ASCII,  Modbus TCP) is supported by many commonly used industrial control devices including PLC, RTU, flow meters, data loggers, and smart instruments; and SCADA Host systems.

The SCADALink SAT50 supporting full bi-directional communication can support Modbus communication to  sites with these remote devices . Note the higher network latency is accounted for and configured in the setup of the SCADA Host; and the messaging frequency is low. The  Modbus register map should be packed so a single poll can transfer the required site status in a single contiguous block.  Multiple message polling of site would not be recommended. WRITE to site registers would have to be infrequent. Communications to Modbus TCP devices onsite can be supported in a Modbus Ethernet to Serial Gateway such as the SCADALink IP100 is used to for protocol conversion.

The SAT50’s support for Modbus Protocol can enable use of many common industrial controller in communications challenged remote site applications. without need for implementation of custom messaging protocols.


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1200 Baud Bell 202 Radio-Modem Replacement

radio modem replacement

1200 Baud Bell 202 Radio-Modem Replacement. There are few instances where technology deployed in the 1980’s is still around, compatible and even usable. 

In the 1980’s, 1200 Baud Bell 202 AFSK based modem systems were commonly deployed for Radio and Wireline Data Communication Systems in SCADA Systems. These systems were robust and long lasting. Many of the Bell 202 based Radio systems utilized mobile radios connected to external Bell 202 modems. Many of these systems are still in use, but they are aging and about to fail.  It is highly recommended to update them before they fail.

The following scenarios will inevitably play out: 1)The two-way radios may fail, and/or 2) the external modem may fail.

Due to product obsolescence there are no plug-in replacements available for the two-way radio or the external modem. So when a site fails, components will need to be repaired in the field or on the bench, however these repairs require expertise in analog electronics. Starting in the 90’s there has been knowledge loss due to retirement of old-time technicians specializing in analog electronics. It is now difficult to find a technicians available with the know-how to repair these legacy systems.

At SCADALink, we have had extensive experience in repair and troubleshooting of aging SCADA systems  – SCADA Communications Troubleshooting.

Emergency Field Repair

We have assisted in emergency field repairs of failing Bell 202 based systems where the 1) Radio Failed, 2) the Bell 202 Modem Failed, or 3) Modulation was out of adjustment.

Repairs were hampered by various factors including:

  • difficulty in compatibility of RF or Modulation levels with replacement equipment
  • lack of documentation of legacy equipment for maintenance
  • lack of availability of replacement equipment
  • connector problems

Network Upgrade Options

There are two ways to deal with this obsolescence problem:

1) Install New Modem Technology with 1200 Baud Bell 202 Compatibility

Systems can be replaced with integrated RF modems that have Bell 202 modulation.
… Modems with Bell 202 Compatibility

One challenge with the type of replacement is that in some installations, the higher RF output of the 25 Watt two-way radios was required to provide adequate fade margin in some data links.

2) Technology Replacement

Alternatively, the obsolete RF Systems can be replaced by new RF technology, either in the same RF band or different bands such as licensed free 900 Mhz, or cellular modem systems. 
..see Replacement Technology