The ICNIRP 1998 and 2010 guidelines for limiting exposure to time‐varying electric and magnetic fields (1HZ – 100 kHz) and specifically about their reference levels for time-varying contact currents from conductive objects brought to the EMF Directive 2013/35/EU, mandatorily in force from July, 1st 2016 in the EU.
One of the parameters to be measured in accordance with this regulation on the minimum health and safety requirements regarding the exposure of workers and general public, is the value of the contact current.
The contact current is a current that flows when a person or an object, acting as an electrical conductor, comes in contact with an object immersed in an electromagnetic field. It is expressed in amperes (A).
Coming into contact with such devices might be dangerous for the worker/operator since the device can accumulate electric charges that can generate a current through the limbs and a contact current through the body. Even an electric machinery not properly shielded can emit electromagnetic waves, so the contact without protection also produces a contact current.
The CCM (Contact Current Meter) developed by MPB greatly simplifies the task of operators who can use it to check the contact current value, so to complete the framework of measurements required by the 2013/35 /EU regulation.
Applications involving contact current can be:
- Industrials ( e.g. induction heating, RF drying, welding and gluing)
- Broadcast pylons maintenance
- Electricity companies’ pylons in proximity to broadcast pylons
- Sources of EMF in hospitals
The CCM works in a range from 40 Hz to 110 MHz and allows acquiring the value of the contact current in two measurement modes:
- Ground mode (GP)
- Hand mode
The Ground Plane (GP) mode is a default mandatory mode to guarantee the safety of the operator. It is in fact performed by using a standardized impedance. After having verified the not dangerous level of the current, The Hand mode allows measuring the contact current by interposition of the human body and, therefore, according to the variable impedance of the operator that performs the measurement.
The output measure from the CCM is the mA value of the contact current, or the percentage in reference to the limit value defined by the standard.