UNICONT PKK–312 series are 4…20 mA current-controlled limit switches featuring galvanic isolation and are also available as intrinsically safe units. The input 4…20 mA signals can be transferred from passive or active outputs of 2 or 4-wire transmitters. The value of the input signal is compared to the set (taught) value, and with comparison mode programming, the state of the galvanically isolated relay changes. 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
■ Monitoring of discontinuity or short-circuit of the cable
■ Window comparison operation mode with energized or de-energized relay state
The UNICONT PKK–312–8 Ex is a special version designed to operate with NIVELCO's Ex rated, DC-powered, 2-wire NIVOSWITCH vibrating fork type level switches as an intrinsically safe power supply and amplifier unit. The galvanically isolated limit switch gives relay-switching signals based on monitoring changes in output current between the free vibrating and immersed states of the vibrating fork without programming.