Human Machine Interface (HMI) has evolved significantly from the days when operations staff had to sit in front of a single screen to monitor a machine or a process. HMI/supervisory control and data acquisition (SCADA) applications now not only monitor and help control equipment and processes, but also provide a huge range of information regarding machine and plant operations.
Since many people consider HMI to be a low-end, panel-mounted apparatus, the term SCADA will be used to refer to the more advanced applications discussed in this article.
Table 1 lists the ways and SCADA systems provide remote access to users. At the most basic, a panel-mounted HMI with built-in web server capabilities provides some limited degree of remote access via a web browser. This access is often only one-way, allowing remote users to view information, but not to make changes.
Modern SCADA systems generally provide server-thin client remote access, allowing any type of PC or other similar device to remotely access the main SCADA system. This type of access is often virtually identical to local SCADA system access, providing a full range of features, albeit at a higher cost than browser or app access.
The next step up is again server-browser access, but this time via local SCADA software, generally running on a PC installed locally at the machine or the process. Although the remote access is still via browser, in most cases this access is more full-featured than with a simple HMI, allowing remote users to view more information in a wider variety of formats. SCADA server-browser access usually provides two-way access, allowing for remote adjustments and corrections.
Many SCADA software packages allow server-mobile phone app remote access. As with SCADA server-browser access, remote users have full-featured, two-way access. But mobile phone app access can provide other advantages, namely easier and faster loading of the remote application and faster response to and from the SCADA system.
Finally, cloud-based SCADA servers can provide multiple means of remote access at very low cost, and are an ideal fit in many applications. This article will discuss all of these remote access methods in detail, focusing on more advanced SCADA-based remote access solutions.
Move To PC-based Systems
Whether it's a plant manager checking the latest overall equipment effectiveness (OEE) performance or an operator reacting swiftly to an alarm, the ability to access data quickly from multiple remote locations makes manufacturers more efficient and flexible. These are some of the advantages of remote access, which are well known to most manufacturers and won't be covered in detail:
* Provides faster operator response to alarms and events
* Allows personnel to leverage their knowledge across multiple facilities
* Improves quality by enabling continuous process improvement
* Cuts costs by reducing or eliminating travel expenses