Zero drift is a slow shift of output at or near zero target-gas concentration over weeks or months—not short-term noise. Ignoring it leads to false alarms, missed alarms, or unnecessary calibrations.
Zero drift vs. span drift and noise
Zero drift is offset near zero concentration, often in ppm or %FS; span drift is gain change at a certified concentration. Baseline noise is fast random variation—do not confuse it with slow drift.
Upward zero drift can trigger false alarms; downward drift delays real alarms. Senseiot datasheets specify both zero and span stability—compare both when selecting.
Root causes by sensor technology
Electrochemical: electrode passivation, electrolyte loss, reference imbalance, temperature effects. NDIR: source/detector aging, dirty optics, thermal effects on path length. MOS: surface chemistry changes, humidity and siloxane exposure.
Installation issues—clogged membranes, EMI, supply ripple—mimic zero drift. Rule out process and electrical causes first. Model specs: product catalog.
What zero drift is acceptable?
Tolerance depends on alarm setpoints. On a 0–100 ppm H₂S unit with a 10 ppm low alarm, +2–3 ppm zero error matters; on 0–1000 ppm CO, ±5 ppm may be tolerable.
Manufacturers cite monthly or annual drift (e.g., ±2 ppm/month). Define SOP thresholds for zero trim vs. span cal vs. cell replacement. Do not mask end-of-life cells with endless forced zeros.
Correct field zero calibration
Ventilate, confirm no target gas, warm up per datasheet, stabilize, then run Zero Cal. With zero-gas cylinders, check leaks and flow.
Avoid zeroing right after alarms, in contaminated air, or before temperature stabilizes. Rapid return after zeroing suggests cross-interference or cell fault. Manuals and training via contact us.
When to replace the sensor instead of re-zeroing
Replace when drift rate accelerates, linearity fails span checks, T90 exceeds spec, self-test flags end-of-life, or after over-range exposure.
Senseiot plug-in cell transmitters cut lifecycle cost with OEM spares and test reports. Request a quote for maintenance kits.