Conductivity meters pass a small electrical current between two electrodes which measures how much electricity the solution is conducting.
Most meters automatically compensate for differences in the temperature of the nutrient solution and are known as ‘automatic’ meters (with manual meters a dial has to be set to the temperature of the nutrient solution).

Conductivity meters are expensive because they contain an advanced micro-processor, but unfortunately this is the only way of accurately measuring the conductivity level

Conductivity meters are generally available in three types:

• Truncheon (with lights indicating the reading).

• Pen (digital reading).

• Probe (separate probe, digital reading).

Like pH meters, these are sophisticated pieces of equipment, and although they are not as delicate as pH meters they still require high levels of care and maintenance.

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

• Do not touch the electrode face as the oils from skin can cause errors of up to 10%.

• Store in a cool, dry place.

• Clean the electrode ends regularly (monthly at least) with a soft scourer and clean off with distilled water.

• Some conductivity meters will need calibrating. How often this needs doing will depend on the quality of the water. In hard water areas they may need calibrating on a weekly basis.