Potential monitoring device – Type 8535


The potential monitoring device Type 8535 monitors potential differences, e.g. between the negative and the grounding conductors in grounded DC railway systems or between the neutral and the grounding conductors to protect against inadmissibly high and dangerous contact voltage.

The low polarity-independent threshold voltage of 24V or 90V and quick response speed of ≤ 2.5 ms at 50 V potential difference guarantee timely shutdown if the return, neutral, or grounding conductor fails or is interrupted.
The large voltage-overload capacity up to max. 1000 V (peak value) ensures the reliable protective function of the monitor.

A bistable zero potential NC contact serves as output. With this output contact, once the control mechanism has been triggered, on-site acknowledgement (after fault correction) is required for reactivation (by pressing “Reset” on the voltage monitor).

To ensure electrical strength and the elimination of environmental influences, the entire circuitry of the potential monitoring voltage is cast.


An interruption of the return conductor, a poor contact, or similar problem causes the potential in the return busbar (e.g. the negative busbar) to increase relative to the grounding conductor. If the potential exceeds the specified threshold value, the bistable output contact opens. This output contact can be reset only by mechanical means after correction of the fault.

An electronically clocked switching amplifier ensures high operating reliability, response speed, and a large operating voltage range with a low power input. State-of-the-art components guarantee a high safety standard and the stability of the individual characteristics and of the monitor overall.

Special electronic circuits enable the device to be optimized for specific applications and tasks.

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