Bluelab Combo Meter | pH, EC and Temperature Meter for Hydroponics Australia

The Bluelab Combo Meter is the most widely used handheld pH, EC, and temperature meter in Australian hydroponics. It measures all three parameters simultaneously in one reading, giving you the complete picture of your nutrient solution without switching between instruments or doing multiple tests. For any grower managing a recirculating system, DWC, NFT, or coco coir feed program, this is the meter most Australian growers trust as their primary tool.

Why Measuring pH, EC and Temperature Together Matters

pH, EC, and temperature are not independent variables. A solution measured at 18 degrees Celsius gives a different EC reading than the same solution at 26 degrees. A pH reading taken without knowing the solution temperature can lead to corrections that push pH in the wrong direction. The Bluelab Combo Meter corrects for temperature automatically using built-in Automatic Temperature Compensation (ATC), which means the EC reading you see reflects the actual nutrient concentration rather than a temperature-skewed number.

This matters more in Australia than in many other countries because our seasonal temperature swings are significant. A Melbourne grow room in summer can see reservoir temperatures 8 to 10 degrees higher than the same room in winter, and that difference changes how nutrients behave in solution. Reading all three parameters simultaneously removes this variable from your nutrient management.

What the Bluelab Combo Meter Measures

pH is displayed on a 0.0 to 14.0 scale with 0.1 resolution. The replaceable double-junction probe is more accurate and longer-lasting than single-junction probes found in cheaper meters, and connects via a standard BNC fitting so it can be replaced in the field when it eventually wears out rather than replacing the whole meter.

EC is displayed in your choice of units: EC (mS/cm), CF, PPM 500 (TDS), or PPM 700. The ability to switch between PPM scales matters because North American feed charts typically use PPM 500 while Australian and European charts use EC or CF. Being able to match your reading format to your feed chart removes a common source of confusion for growers switching between nutrient brands.

Temperature is displayed in Celsius or Fahrenheit and is measured by the same probe as EC. Knowing reservoir temperature at the same time as EC tells you whether a rising EC is caused by plants drinking more water than nutrients (evaporative concentration) or a genuine change in nutrient strength.

How to Get Accurate Readings Every Time

The most common reason Bluelab Combo Meters give inconsistent readings is infrequent calibration. The pH probe drifts over time, particularly in warm grow rooms where biological activity in stored calibration solution can change its reference point. Calibrate with fresh pH 4.0 and pH 7.0 reference solutions at least once per week during active grows, and always after the probe has been stored dry. Store the probe tip in KCl storage solution when not in use to prevent the double-junction membrane from drying out.

Bluelab calibration sachets in pH 4.0, pH 7.0, and EC 2.77 mS/cm are available separately and provide measured single-use portions that eliminate the contamination risk from dipping into a shared bottle repeatedly. For growers who want to verify their EC reading as well as pH, the EC 2.77 sachet confirms the conductivity probe is reading correctly.

Frequently Asked Questions

How often should I calibrate the Bluelab Combo Meter? Calibrate the pH probe at least once per week during active grows. If you are adjusting pH daily and the readings seem inconsistent, calibrate before troubleshooting your nutrient solution. A drifted probe is the most common cause of pH problems that do not respond to correction.

What is the difference between EC and PPM on the Bluelab Combo Meter? EC (milliSiemens per centimetre) is the base unit. PPM 500 and PPM 700 are conversion scales used on different feed charts. PPM 500 = EC x 500. PPM 700 = EC x 700. Most Australian and European feed charts use EC. Most North American feed charts use PPM 500. Use whichever matches your feed chart and do not mix scales when comparing readings.

How long does the pH probe last? Typically 12 to 18 months with regular use and proper storage in KCl solution. The double-junction design extends probe life compared to single-junction alternatives. When pH readings become slow to stabilise or consistently read wrong after fresh calibration, the probe needs replacing. Replacement probes connect via the standard BNC fitting without any tools.

Is the Bluelab Combo Meter waterproof? The probes are designed for immersion in nutrient solution. The meter body itself is splash-resistant but should not be submerged. The 2-metre probe cable allows the meter to sit outside the reservoir while probes are fully immersed.

What is the best pH range for hydroponics in Australia? For most hydroponic systems, 5.5 to 6.5 with a target of 5.8 to 6.2 for the broadest nutrient availability. For coco coir, 5.8 to 6.2. For soil-based indoor growing, 6.0 to 7.0. See our complete guide on why pH keeps dropping in hydroponics for a detailed explanation of pH management in Australian conditions.