OnePen Replacement Probe by Bluelab — pH, EC & Temperature Sensor
BL-MTR-PROBE-ONE
Pairs well with
The Bluelab OnePen Replacement Probe restores pH, conductivity (EC) and temperature accuracy to your Bluelab OnePen in one quick swap. When the probe wears out — or can no longer be calibrated — you replace the sensor, not the whole meter. With a double-junction pH probe and titanium EC electrodes, it brings your OnePen back to the precision it shipped with.
Specifications
- Hydrate the pH glass bulb via the storage cap: place a few drops of KCl storage solution on the sponge inside the cap, fit it, and leave for 24 hours before first calibration. A dehydrated bulb drifts, reads stuck near pH 7 and can break.
- Do not soak the titanium EC electrodes in KCl solution for any length of time — Bluelab warns against it. The cap-sponge method hydrates the bulb without bathing the electrodes.
- Never use RO, distilled or deionised water anywhere near the probe — pure water permanently damages it. KCl only.
- Clean with Bluelab pH Probe Cleaner and a soft brush on the EC electrodes — never Bluelab Conductivity Probe Cleaner, which Bluelab states is not compatible with the OnePen, and never abrasive cleaners.
How to Replace the Probe
Pairs Well With
The 3-in-1 pH, EC and temperature meter this probe belongs to — one pen for the whole reservoir check.
Calibration & pH ControlGrab pH 7.0 and 4.0 calibration sachets plus KCl storage solution — you'll need them to hydrate and calibrate the new probe.
More From BluelabProbes, monitors and meters from the New Zealand brand growers have relied on for over 30 years.
FAQ
Does this probe fit the pH PenPlus or other Bluelab meters?
No. This replacement probe fits the Bluelab OnePen only. The pH PenPlus uses the separate pH ProbePlus, and Combo Meters, pH Meters and Guardian Monitors use BNC-connector probes.
Will a cheaper non-genuine probe work in the OnePen?
No. The OnePen detects and rejects non-genuine probes with a "PROBE INVALID" error — only official Bluelab OnePen Replacement Probes will function.
Does it replace pH, EC and temperature sensing?
Yes. The probe carries all three sensors — a double-junction pH probe, titanium EC electrodes and the temperature sensor — so one swap restores every measurement the OnePen takes.
Do I need to hydrate the new probe before using it?
Yes. Bluelab recommends hydrating the pH glass bulb for 24 hours before initial calibration — a few drops of KCl storage solution on the sponge inside the storage cap, cap fitted. Don't soak the titanium electrodes in KCl, and never use RO, distilled or deionised water.
How long does an OnePen probe last?
Approximately 18 months on average, according to Bluelab. pH probes are charged with reference material that expends through use — good hydration and regular cleaning stretch the lifespan, but every probe eventually fails to calibrate and needs replacing.
Can I use Bluelab Conductivity Probe Cleaner on it?
No. Bluelab states its Conductivity Probe Cleaner is not compatible with the OnePen or this replacement probe. Clean with Bluelab pH Probe Cleaner and a soft brush on the EC electrodes, never abrasives, and recalibrate pH after every clean.
Does calibration solution come included?
No. The probe ships on its own — add pH 7.0 and 4.0 calibration solution and KCl storage solution to your order so you can hydrate and calibrate before first use.
Replace the Probe, Keep the Pen.
Restore pH, EC and temperature accuracy to your OnePen — shipped fast Australia-wide.