Nullpunktdrift

Nullpunktdrift, or zero-point drift, describes a gradual change of the reference level or baseline of a measurement system over time. It results in a systematic offset in the output that is not caused by changes in the measured quantity, effectively shifting the zero point of the instrument. Over time, even with a constant input, the reported value can drift away from the true value.

Causes include aging or degradation of reference components (such as reference electrodes in electrochemical sensors), temperature fluctuations, mechanical effects, supply voltage variations, and intrinsic electronic offset drift in amplifiers and analog-to-digital converters. Sensor membranes may change properties, and drift can be more pronounced in low-signal ranges.

The effects are mainly a gradual bias in measurements, which can mask true trends or produce false signals, particularly in precision instrumentation. It is distinct from random noise or gain drift, which affects sensitivity rather than the zero level. In practice, nullpunktdrift is often observed in pH meters, analytical sensors, and weighing systems, where a maintained zero or baseline is critical.

Mitigation strategies include regular calibration against known standards, zeroing procedures, and two-point or multi-point calibration to separate offset drift from gain changes. Temperature control and compensation reduce thermally induced drift, while high-quality components and stable power supplies minimize electronic offset. In some instruments, auto-zero or drift-correction algorithms estimate and subtract the drift in real time.

In metrology, documenting and correcting for nullpunktdrift is essential for maintaining measurement accuracy over time.