How often should I calibrate Bluelab pH & Temperature Pen?

pH meters should be calibrated before every use or at minimum every 2–3 days during active grows. EC meters are more stable but should be verified against a known reference solution weekly. Bluelab pH & Temperature Pen uses two-point calibration for pH (4.0 and 7.0 buffer solutions) and single-point calibration for EC (2.77 mS/cm standard). Regular calibration is the single most important factor in measurement accuracy.

How do I store Bluelab pH & Temperature Pen properly?

Always store pH probes wet — never allow the probe tip to dry out as this permanently damages the glass membrane. Use the probe storage solution supplied with Bluelab pH & Temperature Pen or Bluelab KCl storage solution. EC probes are more robust but should also be rinsed with clean water after each use. Store Bluelab pH & Temperature Pen at room temperature away from direct sunlight.

What should I do if Bluelab pH & Temperature Pen is reading incorrectly?

First, recalibrate using fresh buffer solutions — old or contaminated calibration fluid is the most common cause of inaccurate readings. Rinse the probe thoroughly with deionised or distilled water between calibrations. If readings are still inconsistent after recalibration, check the probe for physical damage or contamination. Most probes have a service life of 12–18 months with proper care.

Is Bluelab pH & Temperature Pen waterproof?

Check the IP rating listed in the product specifications. Most handheld meters are splash-proof but not designed for submersion. Take care when measuring in deep reservoirs to avoid dropping the unit. Bluelab pH & Temperature Pen is designed for hydroponic nutrient solution testing — it is not rated for outdoor or continuous immersion use.

Does Bluelab pH & Temperature Pen ship fast within Australia?

Yes — Bluelab pH & Temperature Pen ships from our Australian warehouse with fast tracked delivery Australia-wide. Most east coast orders arrive within 2–5 business days. WA, NT, and TAS orders typically arrive within 5–12 business days.

Bluelab pH PenPlus with replaceable double-junction probe, IP68 rated pH and temperature pen

Bluelab pH PenPlus | Replaceable Probe pH & Temperature Pen Australia

Default Title

$184.95

Bluelab pH PenPlus | Replaceable Probe pH & Temperature Pen Australia

$184.95

Quick Answer

The probe unscrews and gets replaced, so a worn probe doesn't mean a new pen.
Double-junction pH probe, temperature in C or F, backlit display, two-point calibration with a 30-day reminder.
IP68 rated, genuinely dustproof and waterproof, not just splash resistant.
Over $150 and 0.25kg, so it ships free to VIC, NSW, QLD, SA and ACT.

Bluelab pH PenPlus

Every pH probe wears out. The glass membrane ages through normal use, readings start drifting, and no amount of calibration brings it back. On a sealed pen that's the end of the pen. The PenPlus is Bluelab's answer to that: when the probe goes, you unscrew it and fit a new one.

Why the Replaceable Probe Changes the Maths

A pH probe generally gives you 12 to 18 months with good care. On a sealed pen, month 18 means buying another pen. On the PenPlus it means buying a replacement ProbePlus and being back to accurate readings in under a minute.

The other thing it changes is downtime. A pen that's drifting mid-grow is worse than no pen at all, because you're making feed decisions on numbers you can't trust. Keeping a spare probe on the shelf means a bad reading is a two-minute fix rather than a week waiting on delivery.

Key Benefits

Replaceable probe. Screw-cap design, swap it out in under a minute with no tools.
Double-junction pH probe. Longer service life than single-junction designs and better resistance to contamination from nutrient solution.
IP68 dustproof and waterproof. Rated for immersion, not just splashes. Dropping it in the reservoir isn't a disaster.
KCl-filled silicone cap. An internal sponge holds the probe hydrated between uses, which is the single biggest factor in how long a pH probe lasts.
Two-point calibration with a 30-day reminder. The pen tells you when it's due rather than leaving you to remember.
Backlit display. Readable in a dark tent without a torch.
Temperature in C or F. Switchable, with the reading shown alongside pH.
Integrated lanyard. With a waterproof silicone probe cap attached, so the cap doesn't go missing.
Auto-off. Powers down on its own to save the battery.

How to Get the Most Life Out of the Probe

Store it wet. That's the whole thing. A pH probe that dries out is permanently damaged, and it's the most common reason probes fail early. The KCl-filled cap on the PenPlus is designed to handle this for you, but the cap needs to actually go back on.

Beyond that, rinse with clean water after each use, clean the probe monthly with a proper probe cleaner rather than wiping it, and calibrate with fresh solution rather than a sachet that's been sitting open. Our Probe Care Kit covers the cleaning and storage side, and the guide to inconsistent readings walks through what to do when the numbers stop making sense.

Technical Specifications

Measures. pH and temperature, simultaneously
Probe. Double-junction, replaceable, screw-cap fitting
Calibration. Two-point, pH 4.0 and 7.0, with 30-day reminder
Temperature Units. Celsius or Fahrenheit, selectable
Ingress Rating. IP68, dustproof and waterproof
Display. Backlit LCD
Hold Function. Yes
Auto-Off. Yes
Probe Storage. KCl-filled silicone cap with internal sponge
Replacement Probe. Bluelab pH ProbePlus, sold separately
Shipping Weight. Approximately 0.25kg

Frequently Asked Questions

How is the PenPlus different from the older Bluelab pH Pen?

The probe. On the older pen the probe is sealed in, so when it wears out the pen is finished. On the PenPlus the probe unscrews and a replacement fits in its place. The PenPlus is also IP68 rated and adds a 30-day calibration reminder.

How long does the probe last before it needs replacing?

Typically 12 to 18 months with proper care, though it depends heavily on how often you use it and whether it's stored wet. Signs it's due: readings drift between calibrations, calibration takes several attempts, or the response gets sluggish.

How do I replace the probe?

Unscrew the old probe, screw in the new one, calibrate. It takes about a minute and needs no tools. Recalibrate immediately after fitting, since a fresh probe won't match the old calibration.

How often should I calibrate it?

Before every use is best practice. At minimum, every few days during an active grow. The pen prompts you at 30 days, but that's a backstop rather than a schedule. Always use fresh calibration solution, since an opened sachet that's been sitting around is the most common cause of a bad calibration.

Can I leave it in the reservoir?

It's IP68 so immersion won't damage it, but it isn't built for continuous monitoring. If you want a meter that lives in the tank, look at the Bluelab Guardian Monitor instead.

How should I store it between uses?

Cap on, probe wet. The KCl-filled silicone cap holds moisture against the probe, and that's what keeps it alive. A probe left to dry out is permanently damaged, not just in need of recalibration.

Does it measure EC as well?

No, this is pH and temperature only. For EC you'd want the Bluelab EC Pen alongside it, or the Combo Meter if you'd rather have both in one unit.

Does it qualify for free shipping?

Yes. At $184.95 and 0.25kg it clears the $150 threshold and sits well under the 3kg cap, so it ships free to VIC, NSW, QLD, SA and ACT. WA, NT, Tasmania and remote areas are quoted separately.