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How To Find SCADA With Good Logging Capabilities

By Ziad Alezabi

February 22, 2024


Your SCADA's (Supervisory Control and Data Acquisition) remote terminal unit (RTU) buffering capabilities are important so you can store data until your Master Station picks it up.

When shopping for a manufacturer that provides you with good SCADA logging capabilities, keep the following questions in mind:

  1. Are you working with a "polling" or an "asynchronous" master station?
  2. What are the benefits of polling vs asynchronous?
  3. Which one best fits your application?
  4. If it is a polling master station, what buffering (in SCADA) capabilities does it have?
  5. Is the manufacturer you're looking at constantly working to improve their logging capabilities?

Let's take an in-depth look at these questions and how to land the right manufacturer that provides you with a SCADA system best suited for you.

Polling Vs. Asynchronous Communication in SCADA Master Stations


It's important to understand the difference between polling and asynchronous master stations when it comes to SCADA.

Polling refers to a master station, from time to time, requesting data from remote terminal units (RTUs) in a sequence.

This would require each RTU to:

  • Have a buffer that stores its data until a master station requests that data from it.
  • Have emergency power backup in case your buffer utilizes volatile memory that is lost during power outages
  • Wait for the master station to check on it. If there is no response, the master station knows the RTU is offline.

This is a useful installation if you work in an environment that requires all RTUs to be online at all times.


Asynchronous master stations on the other hand allow for multiple RTUs to communicate with a master station at the same time.

The great thing about asynchronous master station monitoring is:

  • Its ability to communicate with multiple RTUs simultaneously.
  • It does not need to do it in any specific sequence.
  • You throw away the need for logging capabilities in SCADA altogether.

The negative side of asynchronous RTU monitoring, however, is that you will not be able to tell when a device goes offline.

This is a huge problem, especially if your remote devices are critical to your operations.

Benefits of Polling SCADA

Polling allows for more accurate data collection since it ensures that each RTU is responding and being polled in a specific order.

This also allows for better control and management of multiple RTUs because of the following factors:

  1. Controlled Data Collection: With a polling method, you can control data (via your control system) collection centrally at scheduled intervals. This ensures that your collection method is consistent and reliable.
  2. Simplified Configuration: Polling SCADA has simpler configurations compared to asynchronous setups. You can configure your settings from a single master station which becomes helpful during setup and maintenance.
  3. Predictable Communication: Your SCADA runs on a predictable schedule. This is a plus for network bandwidth management and maintenance purposes because you are working with real-time data.
  4. Compatibility with Legacy Systems in SCADA: Polling SCADA systems are often compatible with legacy equipment and protocols, making them suitable for environments where older hardware and communication standards are still in use. This compatibility allows organizations to leverage existing infrastructure without the need for costly upgrades or replacements.
  5. Polling SCADA systems are compatible with legacy protocols and devices: This allows you to extend your older equipment's usefulness and saves you money that you would've spent installing new equipment.

While asynchronous communication promises you better network security through built-in redundancy in SCADA, a good manufacturer offers you polling SCADA systems that also offer redundancy, which covers both concerns.

Choosing the Right Master Station

Choosing between a polling vs asynchronous master station depends on your specific application's needs. Here are some things to consider:

  1. Do you require controlled and specific data? A polling master station is the best option for you
  2. Do you need predictable, and simple monitoring of your network? A polling station is the best option for you
  3. Do you need redundancy and/or dual redundancy? While asynchronous stations promise this, you can get the same benefit from a polling station with the help of a good SCADA systems manufacturer.

An asynchronous station is good if you are willing to let some interoperability and data logging slip by you. If one of your devices goes offline, you will need separate monitoring to be able to identify it and promptly fix it.

Buffering Capabilities

Whether you choose to go the polling or asynchronous route, you need to consider the logging capabilities and interoperability of the SCADA system that you're looking at.

Building Access System with History Logs

Logging capabilities are the ability to store data in the case of communication failures between the RTU and SCADA master unit due to conditions such as:

  1. RTU malfunction
  2. Master Station malfunction
  3. Power outages
  4. Configuration errors
  5. Software errors
  6. Hardware malfunction

Make sure that you ask your SCADA manufacturer about how big their event buffer is, and for how long it is stored. For example, does it store 100 events on short-term volatile memory? Or is it storing over 10,000 events at a time on non-volatile memory in SCADA?

If it's the first option, you are risking all of your data being lost in the event of a failed dial attempt or power outage.

If it's the second instance, then you are safely storing a large amount of collected data that can also later be combined with AI (artificial intelligence) and used to create:

  • Predictive data (ex. Your industrial plant filter getting clogged causes a heat alarm to go off. Therefore, this heat alarm will go off in two months if you don't clean your filter every 3 weeks).
  • Analysis charts (ex. How often heat alarms occur in correlation to the drier months in your time zone) that aid your industrial automation.
  • History CSV exports

DPS Telecom Covers All Of Your SCADA Communication Needs

DPS constantly strives to improve its SCADA system lineup, including things like:

  1. Communication protocols used
  2. Hardware
  3. Software
  4. Logging capabilities
  5. Interoperability

There was a time when DPS' RTUs stored their data buffers on volatile short-term memory. If the dialer failed to dial the RTUs, the data stored was lost forever.

However, now we have improved RTUs such as the NetGuardian G6 with an M16 interface that writes events to non-volatile memory (close to 10,000 events).

We are excited to develop AI tools. These tools will help you find trends and predict data. This will allow you to run your infrastructure smoothly and efficiently.

If you are interested in the information, have questions, or want to collaborate, please contact me.

Even if we can't find a solution working together, I will do my best to help point you in the right direction.

Give me a call at 1-800-693-0351. You can also send an email to sales@dpstele.com

Ziad Alezabi

Ziad Alezabi

Ziad Alezabi is a Application Documentarian at DPS Telecom. He reviews successful DPS client projects and reports on the best practices that you can use to successfully reach your own project goals.