Voltage Monitoring Relays

Pilz voltage monitoring relays can be used to monitor voltage limit values in single or three-phase supplies, with AC or DC voltage, depending on the technical design.

Single-phase voltage monitoring

The S1UM monitors for voltage values exceeding a threshold limit. On the UP version, the measuring inputs are not polarity-sensitive. If the measured voltage reaches the set response value Uon, auxiliary contact 11-14 changes over and the LED lights. If the measured value falls below the hysteresis value Uoff and automatic reset is selected, the auxiliary contact changes over again and the LED goes out. The unit is ready for operation again. If faults are latched, the unit will not be ready for operation again until an external reset button is operated or the supply voltage has been switched off and then on again.

12 measuring ranges, 0.1 V ... 500 V, selectable
Reaction time can be set to up to 10 seconds
DetectsAC/DC voltage values automatically
Operates to normally energised or normally de-energised mode
Galvanic isolation between measuring and supply voltage
UP version: measuring inputs are not polarity-sensitive
Single-phase voltage monitoring
The ZUZ electronic DC and AC voltage monitoring relay is designed for use with generators, accumulators etc.


In-line connection
Measuring voltage is also the supply voltage
Measuring ranges are determined by the supply
Different operating voltages can be selected
Overvoltage and undervoltage can be set separately
Normally energised mode
Three-phase voltage monitoring

The S3UM voltage monitoring relay is used to monitor overvoltage and undervoltage as well as the phase sequence in 3-phase supplies.


Monitors supplies with and without neutral conductors
Trip device for undervoltage and overvoltage
Evaluates phase sequence
Detects asymmetry
Detects phase failure
Reaction time can be set to up to 10 s
Operates to normally energised or normally de-energised mode

Fault Voltage Monitoring

The PFU6 electronic monitoring relay enables welding transformers to be monitored in accordance with VDE 0545. Hazardous contact voltages / insulation faults are monitored on six measuring circuits. For example, up to six secondary windings on welding transformers can be independently monitored for hazardous voltages, through a single unit.

Its 45 mm housing is designed for a rugged industrial environment, ensuring the PFU6 provides a space-saving solution for the safety of personnel on resistance welding plants, which are used in the automotive industry for example.
Fault voltage monitoring

The PFU6 monitors fault voltages on welding transformers in accordance with VDE 0545.


Also see: emergency stip units, HMI, light curtain monitors, motion control, power monitoring relays, programmable safety systems (PSS), safe bus systems, safety assessment, safety mats, safety relays, safety switches

Monitors voltage of 6 secondary windings on welding transformers
Displays fault voltage and open circuit
Supply voltage can be selected: 24 V...42 VAC/DC or 42... 240 VAC/DC