Bluelab OnePen

Bluelab OnePen pH, EC & Temperature Meter – 3-in-1 Hydroponic Nutrient Tester

The Bluelab OnePen combines three essential nutrient-solution measurements into one professional handheld meter: pH, electrical conductivity (EC) and temperature.

Designed for hydroponics, coco, fertigation, indoor growing and horticulture, the OnePen lets you check pH and EC simultaneously instead of swapping between separate meters. It features high-resolution readings, automatic temperature compensation, a waterproof IP68 design and a replaceable pH/EC/temperature probe for improved long-term serviceability.

Built-in Bluetooth connectivity also integrates the OnePen with Edenic by Bluelab, allowing compatible devices to display live measurements, save data and maintain measurement records.

For growers who regularly check nutrient tanks, feed solutions, source water and runoff, the Bluelab OnePen provides a convenient all-in-one upgrade.

Key Features

• 3-in-1 pH, EC and temperature meter
• Simultaneous pH + EC measurement
• Measures pH from 0.00–14.00
• High-resolution 0.01 pH
• Measures EC from 0.00–10.00 mS/cm
• High-resolution 0.01 EC
• Measures temperature from 0–50°C
• Automatic Temperature Compensation
• Conductivity displayed as EC, mS/cm, CF, ppm 500 or ppm 700
• Replaceable sensor probe
• Double-junction pH probe
• Durable titanium EC electrodes
• Built-in probe health indicator
• Bright backlit display
• IP68 waterproof and dustproof
• Two-point pH calibration
• Bluetooth connectivity
• Compatible with Edenic by Bluelab
• Powered by 2 × AAA alkaline batteries
• Compact handheld design
• Designed for nutrient solutions, water and runoff
• 2-year limited OnePen warranty

Three Essential Measurements in One Pen

Successful nutrient management depends on more than simply mixing fertiliser with water.

Three measurements provide growers with particularly useful information:

pH

pH measures how acidic or alkaline your solution is.

Maintaining an appropriate pH range helps keep nutrients available for uptake by the plant.

EC – Electrical Conductivity

EC provides an indication of the concentration of dissolved ionic salts within your nutrient solution.

It allows growers to monitor nutrient strength rather than relying solely on the amount of fertiliser added.

Temperature

Nutrient-solution temperature influences the root-zone environment and also affects measurement accuracy.

The OnePen measures all three parameters using a single replaceable probe assembly.

Simultaneous pH & EC Readings

A major advantage of the Bluelab OnePen is its ability to display pH and conductivity at the same time.

Available measurement modes include:

• EC + pH
• pH + Temperature
• EC + Temperature
• mV + Temperature when enabled through Edenic

For routine reservoir checks, this means you can immerse one meter and quickly see the two measurements most growers adjust when mixing nutrients.

High-Resolution pH Measurement

The OnePen measures across a 0.0–14.0 pH range.

pH Specifications

Range: 0.0–14.0 pH
Resolution: 0.01 pH
Accuracy at 25°C: ±0.05 pH

The 0.01 pH resolution provides detailed readings for growers who want more precise visibility when adjusting nutrient solutions.

EC, CF, TDS & PPM Measurement

Different nutrient manufacturers and growers use different conductivity scales.

The OnePen supports:

• EC
• mS/cm
• CF
• ppm 500 / TDS
• ppm 700

This means you can select the measurement system that matches your nutrient schedule instead of manually converting between different scales.

Conductivity Specifications

EC / mS/cm: 0–10.00
Resolution: 0.01
Accuracy: ±0.1

CF: 0–100
Resolution: 0.1
Accuracy: ±1

ppm 500: 0–5000 ppm
Resolution: 10 ppm
Accuracy: ±50 ppm

ppm 700: 0–7000 ppm
Resolution: 10 ppm
Accuracy: ±70 ppm

Accuracy specifications apply at 25°C.

Automatic Temperature Compensation

Temperature can influence pH and conductivity measurements.

The Bluelab OnePen incorporates Automatic Temperature Compensation (ATC) to compensate its measurements according to the temperature of the solution.

It also displays the actual solution temperature in either:

°C or °F

Temperature Specifications

Range: 0–50°C / 32–122°F
Resolution: 0.1°C / 0.1°F
Accuracy: ±1°C / ±1°F at 25°C

Replaceable pH, EC & Temperature Probe

One of the strongest features of the OnePen is its replaceable probe assembly.

pH probes are electrochemical sensors and naturally age with use. With some handheld meters, the entire device eventually needs replacing when the sensor reaches the end of its useful life.

The OnePen takes a more serviceable approach.

Its combined pH, EC and temperature probe can be replaced separately, allowing the main meter to remain in service.

The replacement probe incorporates:

• Double-junction pH sensor
• Titanium EC electrodes
• Temperature sensor

A genuine Bluelab OnePen Replacement Probe is available separately.

Double-Junction pH Probe

The OnePen uses a double-junction pH probe designed for durability in nutrient-testing environments.

Regular cleaning, hydration and calibration are still important. Like any quality pH meter, correct maintenance has a significant effect on measurement reliability and probe life.

Titanium EC Electrodes

Conductivity measurements are taken through durable titanium EC electrodes.

These are integrated into the replaceable sensor assembly alongside the pH and temperature sensors, allowing one probe to perform all three measurements.

Probe Health Indicator

The OnePen includes a probe health indicator to help monitor sensor condition.

This provides additional information about the measurement system and can help identify when maintenance or eventual probe replacement may be required.

IP68 Waterproof Design

Nutrient meters are routinely used around tanks, irrigation equipment and wet grow-room environments.

The Bluelab OnePen carries an IP68 water and dust resistance rating, making it well suited to horticultural use.

The waterproof construction provides additional peace of mind when checking reservoirs and nutrient solutions where splashes are unavoidable.

Bluetooth Connectivity

The OnePen incorporates Bluetooth connectivity for integration with Edenic by Bluelab.

When paired with a compatible mobile device, Edenic can be used for functions including:

• Viewing live measurements
• Saving measurements
• Synchronising stored measurements
• Reviewing historical information
• Managing measurement units
• Adjusting compatible OnePen settings
• Synchronising calibration information
• Installing compatible firmware updates

This gives growers the option of maintaining digital records rather than relying entirely on handwritten nutrient logs.

Ideal for Hydroponics & Fertigation

The Bluelab OnePen is designed for testing liquid nutrient solutions and is particularly useful for:

• Hydroponic systems
• Coco
• Run-to-waste irrigation
• Recirculating systems
• Nutrient reservoirs
• Fertigation tanks
• Source water
• Mixed nutrient solutions
• Irrigation solution
• Runoff
• Drain solution
• Greenhouses
• Indoor gardens
• Commercial horticulture

One meter can therefore be used throughout the nutrient-management process.

Simple Nutrient Mixing Workflow

1. Fill Your Reservoir

Begin with your source water and prepare the required volume.

2. Add Nutrients

Add your fertilisers and additives according to your feeding program.

Mix thoroughly.

3. Check EC

Use the OnePen to determine the conductivity of the finished nutrient solution.

Adjust nutrient strength where required.

4. Check pH

Read pH using the same meter and make any required adjustment.

5. Check Temperature

Review nutrient-solution temperature at the same time.

6. Record Your Results

Where desired, use Edenic connectivity to help maintain digital measurement records.

Two-Point pH Calibration

Regular calibration is essential for accurate pH measurement.

The OnePen supports two-point pH calibration, typically using:

pH 7.0 → pH 4.0

Fresh calibration solutions should be used to avoid introducing calibration errors from old or contaminated solution.

Bluelab recommends regular probe maintenance and pH calibration to maintain reliable measurements.

EC Calibration

The OnePen arrives factory calibrated for conductivity.

The EC sensor can also be recalibrated when required using an appropriate 2.77 EC calibration solution.

Keeping the titanium electrodes clean is important for reliable conductivity measurements.

Probe Care & Maintenance

Proper maintenance is particularly important because the OnePen combines multiple sensors into a single probe.

Bluelab recommends:

• Rinsing the probe in fresh tap water after use
• Keeping the pH sensor hydrated
• Keeping KCl storage solution in the storage-cap sponge
• Cleaning the pH bulb regularly
• Cleaning the EC electrodes regularly
• Calibrating pH regularly
• Using fresh calibration solutions
• Inspecting the glass pH bulb for damage

Bluelab recommends cleaning the electrodes and pH bulb and performing pH maintenance approximately every 30 days.

Important pH Probe Storage

The pH sensor should never be allowed to dry out.

Keep the sponge inside the storage cap moist with Bluelab KCl Storage Solution.

Do not use:

• Distilled water
• Deionised water
• Reverse-osmosis water

as a substitute for proper pH probe storage solution.

Also note that the titanium EC electrodes should not be soaked in KCl storage solution. The storage system is designed to keep the pH sensor appropriately hydrated.

What's Included

The Bluelab OnePen package includes:

• 1 × Bluelab OnePen
• 1 × Replaceable pH, EC & Temperature Probe
• 1 × Sensor Cleaning Brush
• 1 × 18mL pH 7.0 Calibration Solution Sachet
• 1 × 18mL pH 4.0 Calibration Solution Sachet
• 1 × Bluelab KCl Storage Solution Sachet

This gives you the essential solutions required for initial pH preparation and calibration.

Technical Specifications

Bluelab OnePen vs Separate pH & EC Meters

The main advantage of the OnePen is convenience without sacrificing the core measurements growers need.

Instead of carrying:

pH Meter + EC Meter + Temperature Meter

you have:

Bluelab OnePen = pH + EC + Temperature

It also provides simultaneous pH and EC display, Bluetooth connectivity and a replaceable combined probe.

For growers who check nutrient solutions frequently, reducing three measurements to one handheld instrument makes routine testing considerably simpler.

Why Buy the Bluelab OnePen?

The Bluelab OnePen is designed for growers who want accurate nutrient management without maintaining multiple handheld meters.

Its combination of pH, EC and temperature measurement covers the fundamental parameters required when preparing and monitoring hydroponic nutrient solutions.

The 0.01 pH and 0.01 EC resolution provides detailed measurements, while automatic temperature compensation helps account for changing solution temperatures.

More importantly for long-term ownership, the OnePen isn't built around a permanently fixed pH sensor. Its replaceable probe assembly means the sensing components can be replaced while retaining the main meter.

Add IP68 protection, titanium EC electrodes, a double-junction pH sensor, probe-health monitoring and Edenic Bluetooth connectivity, and the OnePen provides a modern all-in-one solution for growers who want to take nutrient measurement seriously.

Frequently Asked Questions

What does the Bluelab OnePen measure?

It measures pH, electrical conductivity (EC) and temperature.

Can it measure pH and EC simultaneously?

Yes. Simultaneous pH and EC display is one of the OnePen's key features.

What is the pH resolution?

The OnePen provides 0.01 pH resolution.

What is the maximum EC reading?

The conductivity range extends to 10.00 EC / mS/cm.

Does it display PPM?

Yes. It supports ppm 500 and ppm 700, along with EC, mS/cm and CF.

Does it compensate for temperature?

Yes. The OnePen features Automatic Temperature Compensation.

Is the probe replaceable?

Yes. The complete pH, EC and temperature probe assembly can be replaced separately.

Is the OnePen waterproof?

Yes. It carries an IP68 water and dust resistance rating.

Does it have Bluetooth?

Yes. Bluetooth allows the OnePen to connect with Edenic by Bluelab.

Does it need pH calibration?

Yes. Regular pH calibration is required for reliable measurements.

Does the EC sensor require calibration?

The conductivity sensor comes factory calibrated, but it can be recalibrated when necessary.

How should I store the OnePen?

Keep the pH sensor hydrated using KCl Storage Solution in the storage-cap sponge. Never allow the pH probe to dry out.

Can I store it in RO or distilled water?

No. RO, distilled and deionised water should not be used for pH probe storage.

Can I test nutrient runoff with it?

Yes. The OnePen is suitable for checking nutrient solutions, source water and runoff.

What batteries does it use?

It uses 2 × AAA alkaline batteries.

What is the warranty?

The OnePen carries a 2-year limited warranty, while the replacement probe has a 6-month warranty.