Bluelab Meters and Monitors

Understanding the nutrient solution is an important part of successful growing. Growth Technology’s accurate range of Bluelab meters and testing equipment make this task quick and easy.

Bluelab Combo Meter

The Bluelab Combo Meter is all that is needed for simple and reliable crop management and it’s all within arm’s reach!

The Bluelab Combo Meter is an all-in-one pH, conductivity and temperature meter.

The Bluelab pH Probe and the Bluelab Conductivity/Temperature Probe are simply placed into the solution and the selected reading is displayed on screen.

As the Bluelab Combo Meter is portable and does not require a power supply to operate, it can be used anytime and anywhere to help you manage your crops daily nutrient requirements.

Calibration of the pH is simple with the push buttons on the meter and fresh calibration solutions. Conductivity and temperature do not need to be calibrated as this is locked in during manufacture.


  • Measures pH, conductivity/nutrient (EC, CF, ppm 500 and ppm 700) and temperature (°C, °F)
  • Lightweight and portable
  • Large easy to read display
  • Simple push button pH calibration
  • Successful pH calibration indicator
  • No calibration required for conductivity and temperature
  • Replaceable double junction pH probe
  • Over range and under range indicators
  • Low battery indicator
  • 2 x AAA alkaline batteries included
  • Auto off function

bluelab 5 year..


See first-hand why the Bluelab Combo Meter has everything needed and nothing that isn’t.



Watch how to clean, then calibrate / test the probes for the Bluelab Combo Meter

  • Clean the Bluelab Nutrient/Temperature Probe at least monthly, or even more often if using additives or nutrient solutions that contain oils, as these contaminate the probes and can give an inaccurate reading.
  • Clean and calibrate the Bluelab pH Probe when:

The reading is different to what was expected.

The batteries have been removed or changed.

The pH probe is replaced with a new one or is disconnected from the Combo Meter.

The pH calibration indicators have disappeared.

  • Calibrate the pH every time the Bluelab pH Probe is cleaned, which should be monthly, and use only fresh calibration solutions each time. Large bottles of calibration solution should be de-cantered into small plastic containers. This stops contamination of the solution.
  • Be gentle with the Bluelab pH Probe as they are glass and easily broken.
  • Use Growth Technology calibration solutions to calibrate the pH where possible. These solutions have been specially created to work with the Bluelab product range. Not all calibration solutions are created equal!
  • Place the Bluelab pH Probe storage cap filled with fresh water or Growth Technology pH Probe Storage Solution back over the tip of the Bluelab pH Probe when not in use. This stops the Bluelab pH Probe from drying out. If it dries it dies!
  • Always place the shroud onto the Bluelab Nutrient/Temperature Probe after cleaning to protect the probe face and ensure accurate readings.
  • Be patient with pH. While calibrating or taking readings, wait until the reading has stabilized to a constant value.
  • Wait 5 – 10 minutes for the reading to stabilize if the probe temperatures are very different to the solution temperature and stir the probes in solution or place probes where there is good movement.
  • Remove batteries and disconnect the Bluelab pH Probe if the Bluelab pH Meter is to be stored for long periods of time.
  • Use alkaline batteries where possible.
  • Store in a clean dry place out of direct sunlight


  • Don’t be rough with Bluelab pH Probe or bang it on the side of your tank – it will break!
  • Don’t touch the pH or nutrient/temperature probe heads with fingers. This will contaminate the probe surface. The only time the Bluelab Nutrient/Temperature Probe can be touched is when cleaning the probe with the liquid scourer
  • Don’t use de-ionized or distilled water in the storage cap for the Bluelab pH Probe.
  • Don’t rinse the Bluelab pH Probe in de-ionized or distilled water
  • Don’t use rechargeable batteries.
  • Don’t submerse or drop the Bluelab Combo Meter into any liquid as it is not waterproof. If you do drop it in water, immediately remove the batteries and put in a warm dry place for 24 hours.
  • Don’t throw away the instruction manual. Keep it in a safe place to be referred refer back to it if needed. The cleaning and calibration instructions are in the manual and should always be referred to until the grower is confident that the procedure is being carried out correctly.
  • Don’t open the Bluelab Combo Meter – there are no user adjustments inside. This will void the guarantee. It will show if it has been opened!

Contaminated conductivity/temperature probe – Clean conductivity/temperature probe (see advice tab)

Solution temperature low/high – Wait 5 to 10 minutes for reading to stabilize to constant value.

This is down to the temperature of the conductivity/temperature probe being different to the solution temperature. Wait 5 to 10 minutes for conductivity/temperature probe to reach solution temperature.

pH probe is Contaminated – Clean pH Probe (see advice tab)

Incorrect Calibration – Ensure calibration solutions are accurate. Replace if in doubt. Wait longer for readings to stabilize before calibrating to a constant value

Calibration unreliable – Calibrate pH probe

pH probe damaged or old – Replace pH probe

This is likely due to a broken glass bulb, tube or connector. Check pH probe for damage and replace pH probe if necessary.

There is insufficient power to take a reading. Replace the batteries at once. DO NOT use rechargeable batteries.

It is likely that the batteries are dead or inserted incorrectly. Check batteries are correctly inserted and replace if necessary.

This indicates a problem with the pH calibration. Please read “Section 10” in the BlueLab Combo Meter Manual (error message descriptions).

While in pH Mode – It is over or under the pH range, therefore the solution is > 14.0pH or solution is < 0.0pH. Check the pH probe connection, if this is connected correctly and problem still arises then the pH probe could be faulty.

Whilst in temperature mode this “Ur” message indicates it is over or under the temperature range. The solution is > 51°C / 122 °F or the solution is <0 °C / 32 °F.

While in Conductivity/Nutrient Mode – It is over the range of conductivity/nutrient. This indicates that the solution is > 9.9 EC, 99 CF, 4950 ppm 500, 6930 ppm 700. Note: the conductivity/temperature meter probe or combo meter could be faulty.

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