Pepperl+Fuchs Blog

Selecting the Components of a PCV Data Matrix Positioning System

Posted by Tracy Molnar on Tue, May 21, 2013

What is PCV?

PCV is an absolute linear positioning system.  A continuous band of Data Matrix codes is installed along the application’s travel path. A camera-based read head, typically mounted on the moving part, reads these codes.  Depending on the type of read head, position data is transmitted to the control system using RS485, SSI, or PROFIBUS DP communication.

PCV positioning system
If you’ve decided that such a system is a good fit for your application, you may be wondering how to determine which components you’ll need to get it up and running.  This post is intended to assist you with PCV system component selection.

Basic/required components

There are three basic components required for every PCV system installation:

1. Read head – The camera-based read head is the main component of PCV, and is available in different configurations depending on read range (distance between camera and code band) and output format:

  • Read range – The standard read head range is 80 mm +/- 15 mm (PCV80), which is suitable for most applications.  In certain cases where a longer range is required, we offer a PCV100 read head, which has a 100 mm +/- 20 mm range.
  • Output format – Read heads are offered with SSI, RS485, or PROFIBUS DP interface.  In addition, we offer a non-standard PCV80 read head with LS221 interface, which mimics the output of alternate absolute positioning system WCS.  (Note that while this type of output allows the use of WCS interface modules such as DeviceNet or EtherNet/IP, certain features of PCV that are not compatible with WCS cannot be used.)

2. Data Matrix code band – The standard code band consists of two rows of Data Matrix codes and is delivered in a continuous roll that begins with position zero.  Since it has an adhesive back, no special hardware is needed to install the code band.

3. Shielded cordset or field-attachable connector – Each read head has a built-in connector, so a cordset is required for connection.  The SSI and standard RS485 output read heads have an 8-pin M12 connector (V19), and the LS221 read head has a 5-pin M12 connector (V15).

Optional/recommended components

In addition to the basic PCV hardware, there are several items available that make installation and system setup easier:

  • Bracket – The read head includes four screw holes in the bottom for mounting it directly to the moving part in an application.  We also offer as accessories either a flat or right-angle mounting bracket.
  • Configuration software – There are many parameters that can be set or adjusted in the read head, such as resolution, baud rate, and input/output function, to name just a few.  While the basic settings can be configured using special Data Matrix code cards that are held in the camera’s viewing area to be read in, if you are going to make more in-depth changes to the default settings, or program multiple read heads, we recommend using the PCV Parameterization Tool software.
  • Software interface – To use the software, an interface is required to facilitate the RS232 communication between the read head and the computer running the software.  If you have a read head with SSI output, a second port is included for the interface, and only a connecting cable with power supply is required.  If your read head has RS485 output, there is no second port, and the interface cable must include a serial converter in addition to the power supply.

Optional/application specific components

A few components are available as additional tools that could prove useful in certain applications:

  • Event markers – These short, 1-meter length strips of Data Matrix codes are designed to be placed over the code band in an area or areas where specific processes need to occur, and/or outputs need to be triggered.  Event markers should match the absolute position code band in the number of rows of Data Matrix codes they contain.
  • Read head alignment guide – This tool is designed to attach to the read head and provide a visual indication of optimal spacing between the camera and the code band.
In summary, to use the PCV system, you’ll need a read head, code band, and connection cable.  Many installations also benefit greatly from the use of a read head bracket and Parameterization Tool software (which requires an interface cable and, if the RS485 read head is chosen, a converter).  Finally, a read head alignment guide and/or event marker(s) are available if the application calls for them.

Topics: Positioning Systems

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