Electronic pH meters give a numerical digital reading of the pH level, to either one or two decimal places. They are very accurate and easy to use.

They are very sensitive volt meters which measure the pressure of the electricity of the solution, which is affected by the acidity/alkalinity. Unlike standard electrical volt meters they have amplifiers which increase the power of the probe, as the amounts of electricity being measured are so small.

A nutrient solution will give different pH readings at different temperatures, but good pH meters will compensate for any differences in temperature.

Note that low batteries can give inaccurate readings with both pH and conductivity meters.

They are very sensitive pieces of equipment, and require high levels of care and maintenance, especially in hard water areas, and will need calibrating (page 32) on a regular basis. They can be calibrated either with a mechanical dial or electronically. Meters that calibrate electronically are recommended for very hard water.

CARE AND MAINTENANCE

• Do not totally immerse the meter in the nutrient solution, only the probe end should be submerged.

• Store either in distilled water or a storage solution at room temperature (not in the grow-room).

• Clean probe after each use by rinsing in distilled water.

• Calibrate regularly.