A mis-calibrated analyzer is worse than no analyzer. Routine maintenance is short, cheap and prevents hours of misdiagnosis.
Daily
- Drain water traps before first use.
- Leak test per manufacturer procedure.
- Zero calibration (ambient air).
- Inspect probe for carbon obstruction.
Monthly
- Gas calibration with certified span gas (if supported).
- Replace fine particulate filters.
- Inspect sample hose for moisture / contamination.
- Check NOₓ sensor response against known high-NOₓ vehicle.
Annually
- Full workshop calibration / service (often a legal requirement for MOT use).
- Replace O₂ and NOₓ sensors per manufacturer lifetime spec.
- Replace pump diaphragm / filter pack.
Signs your analyzer is lying
- CO + CO₂ never exceeds 10% on any vehicle (sample path leak).
- NOₓ reads zero on loaded tests (dead sensor or circuit).
- HC floor drifts upward year-on-year (ageing sensor).
- Warm-up takes significantly longer than it used to (pump or heater degradation).
// documentation matters
Keep a calibration log. It's required for MOT accreditation in many jurisdictions and it lets you identify drift trends before they become errors.