Connector Systems

It is well known that 90% of failures in PROFIBUS systems are caused by physical layer (wiring) problems. There are a large number of potential errors and pitfalls to look out for in the layout and installation of PROFIBUS wiring. These are covered on our Certified PROFIBUS Installer course which provides essential training for not only installers but also designers commissioning engineers and maintenance staff.

However, as well as installation training, we can ensure that we use good quality and well designed connectors cable and other network components. Andy Verwer has extensive experience in using various PROFIBUS connector systems in a wide range of industries and environments. Here we explore some of the best solutions that are currently available on the market.

Sub-D Connectors for PROFIBUS DP
Connectors of PROFIBUS DP are available from a number of different suppliers. Not surprisingly, some are better designed than others.

PROFIBUS DP (RS485) 9-pin sub-D connectors are available in a number of configurations. First you must decide whether you are using solid core cable (for static installation) or stranded core cable (where flexibility is required).

Solid core cables are best connected using insulation displacement connectors (also called fast connect, FC). With FC connectors the cable is stripped of the outer sheath to expose the wires and shield, but the individual cores are not stripped. Instead, special blades inside the FC connector pierce the insulation to create a low resistance air-tight connection that will perform well for a long time without problems. Note that it is important that FC connectors are NOT used with stranded cable.

Stranded cables are best wired using screwed or crimped connections. For best performance the wires are individually stripped and fine (0.75mm) boot-lace ferrules are crimped onto the cable.

We can generally choose connectors in a variety of arrangements with 180° (straight cable entry, 90° or 35° entry. It is a really good idea to choose connectors with a piggy back socket for the devices at the ends of every segment this allows health checking and waveform visualisation tools such as ProfiTrace to be connected.

VTC can supply all EPIC connectors at a very cost effective price for FC or screw connectors, with or without piggy-back socket any of the patterns 180°, 90° or 45°.

These EPIC connectors are used on our training courses where they have been rewired many times. They to not last forever, but we have good experience over a period of two years with these connectors in this challenging environment. We also have installed EPIC connectors in a number of factory and process plant installations with good performance and few problems.

Connecting PROFIBUS cable to screw terminals?

As we all should know it is important that the screen of PROFIBUS cables is connected to the local earth at every device. However, PROFIBUS devices sometimes have screw terminals for the bus connection which can make it difficult to connect the cable screen. In the past we often had to bunch the screen into a terminal or even solder a drain wire to the cable screen.

A new simple solution has been introduced by Procentec in the form of a stainless steel grounding clip which is specially designed to connect the screen of PROFIBUS DP (RS485) or PA (MBP) cables to screwed terminals, making a neat and compact solution.

These grounding clips can be purchased from VTC in packs of five. They are not cheap, but worth every penny!

M12 Connectors for DP and PA
M12 connectors have always posed a bit of a problem: Making up cables and connectors on site, getting the screen connected properly and obtaining a water tight connection.

A new M12 connector system from Provertha solves all these problems in one go.