Cleaning your LENS unit
How to clean the probe window and reference cap to keep your LENS unit performing accurately.
Keeping your LENS unit clean is one of the most important things you can do to maintain accurate results. Dirt, smudges, or scratches on the optical surfaces can scatter light in ways that throw off readings — often without any visible error message. This guide walks you through how to clean the two components that matter most: the probe window and the reference cap.
The probe window
The probe window is the small glass surface at the tip of Part A (the probe). When you press the probe against a leaf, the window is the part making optical contact with the sample. Even a thin film of dust, oils, or plant residue on the window can interfere with the light signal passing through it, which will quietly degrade your readings over time.
When to clean it
Clean the probe window at the start of every field session, and any time you notice smudging, fogging, or plant residue on the glass.
What you need
- Mild dish soap (a single small drop)
- Clean, lukewarm water
- A soft, lint-free cloth or lens-cleaning tissue
How to clean it
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Power off the probe. Turn off Part B (probe power source) before handling the probe tip. Never clean the window while the unit is powered on.
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Dampen the cloth. Add one small drop of dish soap to a lint-free cloth or lens tissue, then dampen it lightly with clean water. You want the cloth to be barely moist — not wet enough to drip.
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Wipe in a single direction. Gently wipe the window in one smooth stroke from one edge to the other. Avoid circular scrubbing motions, which can drag debris across the glass and create micro-scratches over time.
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Rinse the cloth and wipe again. Rinse the soap from the cloth with clean water, wring it out, and do one final pass over the window to remove any soap residue.
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Let it air dry completely. Set the probe down with the window facing up and allow it to dry fully before powering the unit back on. This takes about one to two minutes in normal conditions.
The reference cap
The reference cap (Part E) is the white cap you place over the probe tip during calibration. It provides the white reference signal the LENS uses to normalize every scan, so a dirty or scratched cap directly affects calibration accuracy. If your calibration has been drifting or producing unexpected WR readings, the condition of the reference cap is the first place to look.
When to clean it
Inspect the inside of the reference cap before every calibration. Wipe it down any time you see dust, smudges, or debris on the inner white surface.
Removing dust
Use a dry, soft lint-free cloth to gently wipe the inside surface of the cap. Work from the center outward with light pressure. Do not use water or any liquid on the reference cap — the internal coating is sensitive and can be permanently damaged by moisture.
Removing scratches
If the inner surface of the reference cap has visible scratches — hairline marks that don't wipe away — they can be smoothed out with a fine-grit sandpaper.
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Use fine-grit sandpaper only. Use 400-grit or finer. Coarser grits will remove too much material and damage the calibration surface.
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Sand lightly and evenly. Place the sandpaper flat and rub the inner cap surface against it using light, even circular motions. Apply very gentle pressure — you are smoothing the surface, not grinding it down.
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Wipe away all dust. After sanding, thoroughly wipe the inside of the cap with a dry lint-free cloth to remove every trace of sanding dust before using the cap for calibration.
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Recalibrate immediately after. Any time you clean or sand the reference cap, run a fresh calibration before scanning. This ensures your baseline is set from the cleaned surface.
Quick reference
| Component | Issue | Fix |
|---|---|---|
| Probe window | Smudge or residue | Dish soap + water with a lint-free cloth |
| Probe window | Fogging after cleaning | Let dry fully before powering on |
| Reference cap | Dust or debris | Dry lint-free cloth or compressed air |
| Reference cap | Light scratches | Fine-grit sandpaper (400-grit or finer), then wipe clean |
| Reference cap | Deep scratches or worn coating | Contact Picketa support |