New Scan-A-Line Passline Independent Systems

In my recent venture out for a service call, I discovered that many of our faithful customers are unaware of recent developments in our measurement and control technology. A prime example is one of our original customers who is controlling his accumulator loop with one of our Loop Control Processing Units (LCPU) and a 10X-HD40 sensor. We had encountered a problem with a very long analog line back to the PLC that controlled the drive system for the line. The problem was quickly solved and then I began to ask some questions.

Why were they not guiding the line with Scan-A-Line? Had they ever tried to measure strip width on this line? Could there be any cost savings for using either of these applications here.?

As it turns out, the material they were pickling was a rather heavy gage material with very wavy edges. For any guide system to work, it needed to be independent of the strip pass line because of the constantly changing vertical edge positions. When I asked about using our PLI (Pass Line Independent) technology, they were totally unaware of this development.

What is Scan-A-Line’s PLI all about? As the name suggests, PLI enables edge position and width measurements that are independent of the vertical position of the strip. Our Measurement Processing Unit is using a formula from geometry to calculate the intersection of two lines of sight from two separate receivers. Because the positions for each of the receivers, and the positions along the Scan-A-Line LED array are both known, it is possible to find the view line intercepts to calculate the vertical and horizontal position of an edge. This enables a Scan-A-Line system to compensate for changes in pass line of an edge while accurately determining its “X” position across the line. This has implications for Edge and Center Guiding as well as Width Measurement of strips with poor edge shape or a constantly changing pass line.

Our original Pass Line Independent System required a special Scan-A-Line Emitter, with dual video processing circuitry. Although these systems worked very well, they were sometimes difficult to set up because of the LED balance as viewed from two different receivers. The receiver balance problem made them much more susceptible to troubles from misalignment and normal dirt buildup on the lenses.

Two years ago, we undertook a project to solve these problems and improve the PLI system performance. The project was called “The External BR” (binocular receiver) project. This led to two significant improvements to the Scan-A-Line PLI Systems, The first improvement was a method to permit a single video processing circuit to be used with both receivers in a time share arrangement. This makes it possible to use any standard Scan-A-Line Emitter for PLI service. The next improvement was in a program and circuit to permit separate storage of LED balance information for each of the receivers in the system. This improvement eliminated the problems with misalignment and stray lens contamination making the new External BR Systems as easy to install and operate as our original Scan-A-Line systems.

Rather than purchase a whole new sensor system to have PLI, it is now possible to have your existing 10XAS-series sensor upgraded to work as part of a PLI system. With the addition of a second receiver, cable, and a small external circuit to multiplex the receivers, we can turn your old Scan-A-Line sensor into the latest PLI system. The upgraded Emitter will still function as a single 10XAS-series sensor if ever needed as a spare.

Leave a Reply

Your email address will not be published. Required fields are marked *