An EC meter applies an alternating voltage across two or four electrodes and measures the current, giving electrical conductivity. Most include a temperature sensor and report EC at 25 °C. "TDS" or "ppm" meters are EC meters that multiply the result by a conversion factor. Fixed "truncheon" style meters show EC on a scale of lights or markings.
In practice
EC sensors are far more robust than pH probes: no glass bulb, no storage solution, and they hold calibration much longer. Calibrate every few weeks or after cleaning with a standard such as 1.413 mS/cm, and check against it if readings look odd.
Keep the electrodes clean. Rinse after use, and occasionally clean with mild soapy water or a dilute acid to remove nutrient films. Make sure no air bubbles sit on the sensor face when reading, and stir gently.
Pick a meter that shows mS/cm, not only ppm, so your numbers translate to research and charts.
Don't confuse with
- pH meter: measures acidity; different sensor, different care.
- Substrate EC sensor: inserted into the medium to read pore-water EC, often with moisture; values differ from runoff EC.
EC (electrical conductivity) measures how well a solution conducts electricity, a proxy for total dissolved salts; growers read it in mS/cm to gauge nutrient strength.TDS (total dissolved solids) is the mass of dissolved material in water; grow meters estimate it from EC with a conversion factor and display it as ppm.The conversion factor is the multiplier a TDS meter applies to EC to report ppm, commonly 0.5, 0.64 or 0.7; it is why ppm readings differ between meters.pH measures how acidic or alkaline a solution is on a 0–14 scale; in growing it controls nutrient uptake, with soil best near 6.0–7.0 and hydro 5.5–6.5.mS/cm (millisiemens per centimetre) is the standard unit of EC for nutrient solutions; 1 mS/cm equals 1 dS/m and 1,000 µS/cm.NFT (nutrient film technique) runs a thin, continuous film of nutrient solution along sloped channels, with roots resting in the stream and exposed to air above.A pH meter measures solution pH with a glass electrode whose voltage changes with hydrogen ion activity; it needs regular calibration and a moist probe.Runoff is the water or nutrient solution that drains out of the bottom of a container after irrigation; growers test it to see what is happening in the root zone.A calibration solution is a standard liquid of known pH or EC used to calibrate meters, such as pH 4.01, 7.00 and 10.01 buffers or 1.413 mS/cm EC standard.ATC (automatic temperature compensation) is a meter feature that corrects pH or EC readings for sample temperature, usually referencing EC to 25 °C.
