Step 1 — Dry calibration

Probe must be completely dry, out of any liquid. Required first; sets the open-circuit baseline.

Step 2 — Low point

Submerge probe in 12,880 µS/cm calibration standard. Wait ~1 min for the live reading to stabilise.

Step 3 — High point

Rinse probe with deionised water first. Then submerge in 80,000 µS/cm standard. Wait ~1 min.

Step 4 — Enable salinity output

Adds the S field (PSU 0–42) to the probe's reading. EZO output stays the same otherwise.

Step 1 — 100 % saturation

Pick whichever of the three is easiest. All three produce the same saturated-air environment the optical probe needs. Writes 0x0002 → 0x1010.

• Field method (deployed buoy): lift the probe out of the ocean until the optical face is 1–5 cm above the water surface. Shake off droplets. The air above the sea is naturally water-saturated and at exact sea-level atmospheric pressure — these are the canonical conditions.
• Bucket method (lab quick): half-fill a jar with tap water, hold probe ~1 cm above the surface inside the jar with a loose lid. Wait ~5 min for the headspace to equilibrate.
• Datasheet method (lab strict): aerate distilled water for 1 hour with an air pump, sit 30 min, hold probe ~1 cm above. Most accurate but slow.

Wait for the live DO saturation reading above to stabilise (1–2 min) at a value near 100 %, then press the button.

Step 2 — Zero point

Prepare zero-oxygen solution: 5 g anhydrous Na₂SO₃ + 95 g distilled water, let sit 1 hour. Submerge probe, stir gently, wait for reading to drop and stabilise (1–2 min). Writes 0x0001 → 0x1010.

Salinity compensation (register 0x1020)

Set the salinity the probe should assume when converting sat % → mg/L. Default 30 ‰ for seawater; set to 0 for fresh-water lab work.

Atmospheric pressure (register 0x1022)

Stored as kPa × 100. Sea-level default = 10133 (101.33 kPa). Adjust for altitude or local barometric reading.