• Electrical connection is only permitted to authorised technicians;
• When assembling and connecting the controller and at choice of the used line material, the valid VDE 0100 regulations "regulations for the establishment of high voltage systems with rated voltages under 1000 V" are to be observed;
• When switching contactors and other inductive load, malfunctions can occur, and in extreme cases damage of the controller. We recommend to provide cut-out relay coils with spark-stopping components;
• The controller and the corresponding installations contain live parts. Under no circumstances must the housing be opened by the user. At possible contact with live parts, the equipment is to be separated 2-pole from the net;
• All sensor and signal lines should be locally separated from control and mains voltage lines, and not be parallel laid, in order to avoid capacitive or inductive linking. If possible, shielded measuring lines are to be used;
• The controller is to be grounded with protective ground wire. In order to avoid earth loops and irritating currents, a common ground connection is to be provided for all ground lines, which is connected with the shielded line of the voltage supply (no ground lines between different controllers);
• No further consumers are to be connected to the net clamps of the controller;
• Do not operate controllers in environment with risk of explosion.

The use of microprocessors and regulations units allows complex tasks to be carried out without loss of operating flexibility and supervision. As the variety of tasks gets larger and measuring accuracy becomes more critical, however, susceptibility to interference similarly increases.
VDE 0843 provides a European standard for the electromagnetic compatibility (EMC) of measuring, control and regulation devices for industrial process technology. Among other things, this standard lays down the interference levels which a device can be expected to tolerate.
For the trouble-free operation of an installation, the interference should be well below guidelines. It is well-known, however, that far higher interference levels may occur in industrial practice where sources of interference cannot be completely eliminated. An unsuppressed contactor can easily generate interference-voltage impulses of 3 kV.

Interference can be spread through wiring or via electro-magnetic radiation. The effects most damaging to control systems are normally the result of wire-borne interference. Possible sources of interference are:

• contact bounce when switching loads
• switching off inductive loads (contactors, motors, solenoid valves, …)
• unfavourable wiring paths
• wire cross-sections too small
• loose connections
• switched power supplies (power converters, …)
• phase controllers, speed controls
• isolating switches
• high frequency generators

Some basic principles must be observed for the installation of processor controlled regulation systems:

1. Keep sources of interference to a minimum, i.e. carry out suppression measures and keep interference levels as low as possible (VDE 0875 prescribes suppression to b e carried out in accordance with VDE 0874). As a basic principle, interference must be suppressed at the point where it arises.
2. Locate unavoidable sources of interference as far away from the control systems as possible.
3. All sensor and signal lines should be spatially separated from control and mains-voltage cables. Capacitive or, possibly, inductive coupling might lead to cross-talk from high-voltage cables to low-voltage lines installed parallel to them, falsifying measurement values and signals or even interfering with the control process.
4. Use screened measuring lines and earth the screening. Wherever possible, us only the common earth connection and make sure that there is no second earth connection (at the controller, for instance) to cause non-permissible ground loops giving rise to stray currents. The measuring points of many thermocouple sensors are in contact with their sheath and screening. In these cases the controller must not be earthed to the screening.
5. The installation of a separate power supply cable for the control system is recommended. This reduces interference levels transferred via the mains cable, and voltage drops caused by the switching of large loads are less noticeable.
6. If inductive loads such as contactors and solenoid valves are switched, induction voltages caused by switching should be reduced by suitable protection measures. These measures are dependent on whether DC or AC voltages are involved:
   In the simplest cases in DC networks, a recovery diode with a high resistance to surge currents can limit the induction voltage.
   For alternating voltage operation, an RC filter is often used. It must be placed to suite inductivity. The filter values can either be calculated, provided that the inductivity of the coil is known, or they can be found by experiment. Only capacitors approved to VDE 0565 are to be used.
7. Semiconductor switches (thyristors, triacs SSRs) generate interference voltages due to their non-linear characteristic curve and their finite gate-trigger voltage. Because of their limited blocking voltage, however, they themselves have to be protected against overvoltage. Here, varistors, RC combinations or chokes are often used. Where semiconductor switching is employed, zero-voltage switches should be used whenever possible.
8. A mains filter should be used to protect the controller against severe mains power supply interference. The filter should be fitted as close to the controller as possible and be connected by short safe-to-touch leads. It is of paramount importance that the mains filter is earthed. Please note that a small current will flow through the filter circuit at all times.

The mains power to consumers switched by the controller must never be supplied from the controller side of the mains filter.

All measures taken to suppress interference will also prolong the life of the components and consequently that of the plant. RC filters reduce contact erosion and increase contactor life.

These instructions are only suggestions and they are not complete. If you want further information please contact the manufacturers of switching elements. Usually, these manufacturers also sell units for interference suppression. You may also contact manufacturers of interference suppression devices:

Lütze GmbH, Weinstadt
Murata Elektronik GmbH, Nürnberg
Murrelektronik GmbH, Oppenweiler
Schaffner Elektronik GmbH, Karlsruhe
Timonta Manger GmbH, Freiburg
VAC Vacuumschmelze GmbH, Hanau

The filter should always be adapted to the inductivity. The following typical component is available and recommended: RC filter, 50 R + 0,1 µF, 115/230 V~
Order no.: 900089.008

Mains filter with slip-on terminal, 230 V~
Order no.: 900089.002

• Environmental conditions indicated in the technical data must be observed.
• Permissible ambient temperature at storage: -20°C...+70°C
• Permissible ambient temperature durng operation: 0°C...+55°C
• Maximum relative humidity: 75% without moistening
• Maximum mechanical load: 2m/s² (sliding sine)

Cleaning the front foil common commercial cleaners (e.g. detergents) are to be used. Organic solvents (e.g. kerosene or spirits) and high pressure cleaners are to be avoided.