Bluelab® OnePen — pH, Conductivity (EC) & Temperature with Replaceable Probe

Three Measurements, One Probe, One Click

Carrying separate pH and EC meters means twice the probes to maintain and twice the chances of leaving one in the wrong room. The Bluelab OnePen measures pH, electrical conductivity, and temperature from a single replaceable probe, capturing all three with one button press instead of switching between instruments.

Its slim pen shape fits a shirt pocket or tool belt for grow room rounds, and because the probe is replaceable, a worn probe can be swapped out without buying a new pen.

Key Features & Benefits

• Three-in-one measurement — pH, EC, and temperature from a single probe insertion.
• Replaceable probe — swap a worn or damaged probe without discarding the whole pen.
• One-click data capture — a single button press records a reading, reducing testing time.
• Compact pen form factor — fits a shirt pocket or tool belt for facility rounds.
• Temperature compensation — built-in temperature measurement supports accurate EC readings across solution temperatures.

Who Should Use This

Growers, nutrient solution managers, and technicians who need fast pH and EC checks across multiple reservoir or fertigation points, and prefer one pen over two separate meters, are the direct fit.

About Bluelab Corporation

Bluelab, a New Zealand company with more than three decades in pH and conductivity measurement, built the OnePen as its combined single-probe pocket meter.

Frequently Asked Questions

How often does the OnePen probe need replacing?

Replacement frequency depends on usage intensity, solution types, and storage practices. With regular calibration and correct storage, Bluelab probes commonly last on the order of 12 to 24 months under frequent-use conditions.

What calibration solutions does the OnePen need?

pH calibration uses Bluelab pH 4.0 and pH 7.0 solutions, or pH 7.0 and pH 10.0 depending on your working range. EC calibration uses Bluelab 2.77 EC standard solution.

Does the OnePen log data over time?

The OnePen features one-click capture of a single reading at a time. For ongoing data logging and trend analysis, pair it with a compatible data management workflow rather than relying on the pen alone.

How do I care for the probe between uses?

Rinse the probe with clean water after use and store it in Bluelab KCl storage solution or a pH 4.0 calibration solution to keep it hydrated. Replace the probe if readings begin to drift noticeably between calibrations.