Junction Box for Fieldbus (Foundation Fieldbus, Profibus), HART and conventional instrumentation (4-20mA)

JM400 is junction box, specially designed to make easier fieldbus connections (FOUNDATION™ fieldbus, PROFIBUS), HART and conventional instrumentation 4-20 mA. The IP66/68W housing protection, combined with appropriate cable glands, protects the wire connections from dust, water, oil, and moisture. It may be used indoors or outdoors and can withstand the most severe environments.

The JM400 design allows an easy access to the terminals, without using special tools. The terminals are twin type at the four ends. They can be used as the input and output of the bus according to the application convenience, keeping apart the wires that should be disconnected in case of device maintenance. This arrangement makes possible the disconnection of devices without disrupting the continuity of the whole segment.

  • Allows easy and safe device connections to the fieldbus (FOUNDATION fieldbus, PROFIBUS), HART and also conventional instrumentation (4-20 mA).
  • Ideal for coupling sensors, actuators and measuring instruments in hazardous areas or not.
  • During maintenance prevents short-circuiting to the entire bus.
  • Allows disconnecting devices without disrupting the continuity of the bus.
  • Reduces wiring costs as well as minimizes design costs of the process control system.
  • Reduces the startup time and simplifies electrical maintenance. Reduces the time of stops.
  • The weather proof housing prevents water, oil and dust from reaching the electrical connections.
  • 4 inputs/outputs connections may be used according to the application convenience.
  • Easy internal bus terminator accommodation.
  • Aluminum and stainless steel construction.
  • Cover’s locking mechanism.
  • External grounding terminal.
  • Does not require lugs.
  • Spurs have protection against short circuits on the JM400-C3.


The JM400-C3 offers protection against short circuits in the spurs (between + and – terminals), limiting the current to 50 mA on each. Thus, the short circuit does not propagate between the spurs nor in the main trunk. This option has short circuit indication LED and built-in terminator.

In normal operation, each protection short-circuit has less than 1 mA of current consumption. After removing the short-circuit, the spur goes to normal operation and the protection circuit is disabled, turning off the LED.


Technical Specifications of JM400-C3

  • Physical layer: according to IEC 61158-2, bus-powered 9-32 Vdc
  • Application: for Profibus-PA and Foundation fieldbus
  • Maximum Trunk Current: 2.5 A
  • Quiescent current per spur in normal operation: <1.0mA
  • Maximum current during a short-circuited per spur: 50mA
  • Maximum drop voltage per spur: 0.3V @ 20mA
  • Number of spurs: 2
  • Terminator: 100 Ohm resistor and 1uF capacitor selectable by a switch
  • Short-circuit status: through a LED: On (red) spur in short-circuit condition; Off: spur in normal operation
  • Spur Connecting: Removable terminal blocks with screw 3-way 2.5 mm ²
  • Housing Material: Aluminum
  • Cover: 4 screws with o’ring
  • Mounting: for field mounting
  • Degree of protection: IP 66/68
  • Operating Temperature: -20 ° C to 70 ° C
  • Storage: -40 ° C to 85 ° C
  • Relative Humidity: 0-95% non-condensing
  • Explosion proof: CEPEL certification

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