The PKK-312 is a 4–20 mA switch with galvanic isolation.
The product range includes an intrinsically safe version.
The input signal value is compared with the setpoint value, and the galvanic isolation's state changes according to the programmed comparison mode.

The outputs can be programmed for the following applications:

• Switching threshold (high or low)
• On/off control with selectable switching hysteresis
• State comparison mode with relay activation or deactivation
• Line break or cable fault monitoring

Instead of the 4–20 mA signal, a dry contact can also be connected to the input.
The state of this contact will be mirrored and the output signal will remain galvanically isolated.
The PKK-312 includes circuitry allowing selection of delays: 0.1, 1, 2, or 5 seconds.

Relay state diagram:

The relay's operating modes can be configured using the front-panel keys, with guidance from the dual-color LEDs.
One of the key settings is the relay operating mode “R”:

When the input current exceeds the threshold setting:
If R = 1, the relay output is activated
If R = 0, the relay output is deactivated

Thus, for fill/drain or temperature maintenance applications, the control mode (normal or inverted) can be freely assigned to on/off function.