blivet

A blivet is a negative-going transient that appears on a signal line carrying a high or logic-1 voltage. For a duration typically measured in microseconds or less, the signal drops to a low or logic-0 state before snapping back to high. In power systems and control circuits, these spikes occur on lines that spend most of their time at nominal voltage, making the blivet look like a momentary fault or glitch rather than a sustained condition.

Blivets commonly originate from switching transients in semiconductor circuits, relay contacts opening or closing, or coupled noise from adjacent high-frequency signals. A relay contact breaking can create a blivet on the control voltage line as the arc extinguishes and the circuit re-establishes. Transformer saturation, capacitive coupling between power and signal paths, and ground bounce in digital logic also generate them. The spike's amplitude and duration depend on the source impedance, the circuit's inductance and capacitance, and the speed at which the transition occurs.

Detection and consequences

Blivets matter because they can trigger false state changes in sensitive circuits. A protective relay or logic gate sampling the signal during the spike might misinterpret it as a valid low pulse and initiate unintended shutdown or switchover. Microprocessor inputs, analog-to-digital converters, and opto-isolated signal receivers are particularly vulnerable. Industrial equipment tolerates the occasional blivet, but in fast-switching applications or high-reliability systems, they must be filtered or inhibited.

Suppression relies on signal filtering using RC networks, ferrite clamps, or varistors placed close to the source. Many control systems add logic hysteresis or pulse-width discrimination to reject transients shorter than a specified threshold. Shielded cabling and careful grounding layout reduce coupling from adjacent conductors. The term, which has no clear industrial etymology, is sometimes spelled as a variant of the electronics term for an undefined or embarrassing nonsense object, reflecting its nature as an unwanted artifact rather than a designed feature.

In utility protection and SCADA systems, blivets on status and trip signals are addressed through contact debouncing circuits or programmable delays that ignore pulses briefer than 10 to 50 milliseconds. Failure to account for them in vintage systems upgrading to faster microprocessor-based controls has caused nuisance tripping and spurious alarms on aging plants where wiring and relay timing assumptions no longer hold.