RS-485 interface isolation and surge protection device ISPD-485

ISPD-485 device is used for isolation and surge protection of RS-485 interface lines. The ISPD-485 is installed in the RS-485 line to protect equipment from high-voltage impulse interferences caused by:

• lightning discharges
• radiation from industrial equipment
• various electromagnetic fields

Lightning protection is provided due to application of the following components in the electronic circuit board of the ISPD-485 device:

• Gas discharge tube - provides primary protection, accepts and dissipates powerful impulse interference. When triggered, it provides very low impedance and high current carrying capacity, safely diverting the interference pulse to ground.
• TVS diode - protects the device input from fast nanosecond interferences and electrostatics at a time when the gas discharge tube has not yet had time to trigger due to its inertia.
• Optical isolation - an electrical signal is supplied to the input of the LED, which transmits it through a dielectric insulation barrier to a photodiode, which converts it back into an electrical signal. Thus, preventing the high-voltage pulse from passing further along the circuit.
• Galvanic isolation - transfer of energy or information signal between electrical circuits that do not have direct electrical contact between them. Galvanic isolation is used to transmit signals in order to reduce interference, for contactless control and to protect equipment from damage and people from electric shock.

The ISPD-485 can work in different areas. Once of its applications is installation on petrol stations in between the PTS-1/PTS-2 forecourt controllers and other forecourt equipment (fuel dispensers, ATG probes, price boards, readers, others) in order to isolate and protect input circuits of forecourt controllers from external harmful influences.

Notes:

• ISPD-485 device has 4 independent protection lines
• make sure to make connection correctly:
  • ports named PTS are intended for to connection to the protected equipment
  • ports named External are intended for to connection to the RS-485 lines
• earthing terminal is intended for connecting the ground. Connecting to the ground is mandatory for protecting of the RS-485 ports!