PKK-312 series is a 4 ... 20 mA current controlled limit switch featuring galvanic isolation also available as anintrinsically safe unit. The value of the input signal will be compared in the unit with the set (teached) value and the state of the galvanically isolated relay changes in accordance with the comparison mode programmed. The double throw output relay can be programmed for the following functions:

• Limit switch (high or low fail safe)
• ON-OFF control with selectable switching difference.
• Window comparison operation mode with energised or de-energised relay state.
• Monitoring of discontinuity or short-circuit of the cable.

Instead of the 4 ... 20 mA current a dry contact can also be connected to the input. The state of this contact will be copied and the output signal will be galvanically isolated. The circuitry incorporated in the PKK-312 enables delayed switching, a switching delay of 0.1, 1, 2, and 5 can be selected.
The PKK-312-8 Ex is a special version, engineered to co-operate with Ex rated vibrating fork level switch, as an intrinsically safe power supply and amplifier unit.