Bluelab OnePen Replacement Probe – Replacement pH, EC and Temperature Sensor

The Bluelab OnePen Replacement Probe is a genuine replacement sensor designed to restore reliable pH, electrical conductivity (EC), and temperature measurements to the Bluelab OnePen. Instead of replacing the entire testing instrument when its original sensor becomes worn or damaged, growers can install a new probe and continue monitoring their nutrient solutions with confidence.

Engineered with a double-junction pH electrode and durable titanium EC electrodes, this replacement component provides accurate measurements for hydroponic systems, greenhouse production, indoor cultivation, and professional horticulture.

Its easy-to-replace design minimizes equipment downtime, while its IP68 waterproof and dustproof rating makes it suitable for regular use in demanding growing environments.

Designed specifically for the Bluelab OnePen, this replacement probe offers a practical way to maintain measurement accuracy, extend the useful life of the instrument, and reduce unnecessary equipment replacement.

Three Essential Measurements in One Replacement Probe

The Bluelab OnePen Replacement Probe combines three measurement functions in a single replaceable sensor assembly.

pH Measurement

The double-junction pH electrode measures nutrient solution acidity and alkalinity, helping growers determine whether conditions support appropriate nutrient availability.

Electrical Conductivity (EC)

Titanium conductivity electrodes measure the electrical conductivity of nutrient solutions, providing information about dissolved nutrient concentrations.

When installed in the Bluelab OnePen, EC measurements can also be displayed using supported conductivity scales, including CF, ppm 500, and ppm 700.

Temperature Measurement

The integrated temperature sensor allows growers to monitor nutrient solution temperature in Celsius or Fahrenheit.

Temperature monitoring provides useful information about reservoir conditions and supports temperature-compensated measurements.

Key Features and Benefits

• Genuine Bluelab Replacement: Designed specifically for the Bluelab OnePen.

• Three-in-One Sensor: Measures pH, electrical conductivity, and temperature.

• Double-Junction pH Electrode: Provides durable pH measurement technology suitable for regular nutrient solution testing.

• Titanium EC Electrodes: Corrosion-resistant electrodes designed for dependable conductivity measurements.

• IP68 Protection Rating: Waterproof and dustproof construction for demanding horticultural environments.

• Easy Replacement: Allows growers to replace the sensor without purchasing a complete OnePen.

• Accurate Measurements: Restores the instrument's measurement capabilities when correctly installed, cleaned, and calibrated.

• Reduced Equipment Downtime: Convenient installation helps growers resume regular testing quickly.

• Maintainable Design: Supports routine cleaning, calibration, and appropriate probe hydration.

• Cost-Effective Maintenance: Helps extend the useful life of existing Bluelab OnePen instruments.

Compatibility with the Bluelab OnePen

The Bluelab OnePen Replacement Probe is designed specifically for the Bluelab OnePen multiparameter testing instrument.

Once installed, the probe works with the OnePen's built-in measurement and display functions, including pH, conductivity, and temperature readings.

The OnePen can also connect to the Edenic by Bluelab app through Bluetooth for supported measurement recording and data management features.

Important: This product is a replacement sensor only. The Bluelab OnePen testing instrument is sold separately, and the replacement probe does not function as an independent meter.

How to Replace the Bluelab OnePen Probe

Replacing the sensor is a straightforward process that does not require replacing the complete instrument.

Step 1 – Remove the Protective Cap

Carefully remove the storage cap from the Bluelab OnePen.

Step 2 – Remove the Existing Probe

Turn the instrument upside down to help keep the batteries in place. Unscrew the threaded retaining collar and gently remove the existing probe from the pen body.

Step 3 – Install the New Probe

Remove the protective cap from the replacement probe.

Align the arrow on the probe with the corresponding notch on the OnePen housing, then insert the sensor fully into position.

Step 4 – Secure the Probe

Reinstall the threaded retaining collar and tighten it securely without overtightening.

Step 5 – Calibrate and Verify

Calibrate the pH sensor using fresh calibration solutions according to Bluelab's instructions.

Check the conductivity measurement using the appropriate Bluelab EC reference solution before returning the instrument to regular use.

Technical Specifications

*Measurement ranges, resolution, and accuracy reflect the specifications of the complete Bluelab OnePen when fitted with a compatible, properly maintained replacement probe.

Maintenance and Probe Care

Proper maintenance is essential for preserving measurement accuracy and maximizing the useful life of the Bluelab OnePen Replacement Probe.

Bluelab recommends cleaning the pH bulb and EC electrodes regularly, with monthly maintenance serving as a general guideline.

After each measurement, rinse the probe with clean water to remove nutrient residues. Use cleaning products and procedures specifically approved for the OnePen sensor.

The pH electrode must remain hydrated during storage. If the sensor accidentally dries out, Bluelab recommends rehydrating the pH bulb in KCl storage solution for approximately 24 hours before recalibrating.

Never store the pH electrode in distilled, deionized, or reverse-osmosis water.

The manufacturer's estimated average probe lifespan is approximately 18 months, although actual longevity depends on usage, cleaning, storage, and calibration practices.

When Should You Replace Your Bluelab OnePen Probe?

Regular cleaning and calibration can resolve many measurement issues. However, replacement may be necessary when the sensor reaches the end of its useful life.

Common warning signs include:

• Persistent calibration failures despite proper cleaning and hydration.
• Unstable or inconsistent pH measurements.
• pH readings that remain near 7.0 regardless of the tested solution.
• Visible damage to the glass pH electrode.
• Repeated measurement problems that cannot be corrected through recommended maintenance.

Replacing the probe allows growers to restore the OnePen's measurement functions without purchasing an entirely new device.

Frequently Asked Questions About the Bluelab OnePen Replacement Probe

What does the Bluelab OnePen Replacement Probe measure?

The replacement probe measures pH, electrical conductivity (EC), and temperature when installed in a compatible Bluelab OnePen instrument.

Is the replacement probe compatible with other Bluelab pens?

The Bluelab OnePen Replacement Probe is specifically designed for the Bluelab OnePen. Compatibility with other Bluelab instruments is not indicated by the manufacturer.

Does the replacement probe include the complete OnePen meter?

No. This product includes the replacement sensor only. The complete Bluelab OnePen is sold separately.

How long does the Bluelab OnePen Replacement Probe last?

Bluelab indicates an average service life of approximately 18 months. Actual lifespan varies depending on frequency of use, cleaning, calibration, and proper storage.

Does a new replacement probe require calibration?

Yes. After installation, follow Bluelab's calibration procedure using fresh pH calibration solutions. Conductivity readings should also be checked using the recommended EC reference solution.

How should I store the replacement probe?

Keep the pH bulb hydrated with appropriate Bluelab KCl storage solution and follow the manufacturer's storage instructions. Never allow the glass pH electrode to dry out.

What should I do if my OnePen will not calibrate?

Clean the sensor, ensure the pH electrode is hydrated, and recalibrate using fresh solutions. If calibration continues to fail or the glass electrode is damaged, the replacement probe may need to be changed.

Does replacing the probe affect Bluetooth connectivity?

No. Bluetooth connectivity is a function of the Bluelab OnePen instrument itself. Installing a compatible replacement probe allows the meter to continue using its supported Edenic app features.