The Bluelab Conductivity Pen simply tells you that your plants have the right amount of nutrient in your solution and lets you know if adjustments are needed. To feed plants well, we need to know what we're feeding them. The Conductivity Pen provides quick and accurate EC or ppm readings at the click of a button, so you can rest assured you will have reliable results, every single time.
The EC pen is also known as a TDS meter, and can provide measurements in PPM, EC and CF.
 
Bluelab Conductivity Pen Benefits and Features
Fully waterproof, not just water-resistant - will even float when it lands up in your reservoir.
Selectable measurement units so you can customise with your preferences
Flat electrode for easier cleaning and maintenance
Hold reading function to capture every measurement with ease
Automatic temperature compensation for accurate readings anywhere
Auto-off function to extend battery life
1 x AAA alkaline battery included, getting you started immediately
Designed and built in New Zealand with growers, for growers - the Bluelab Conductivity Pen can handle the knocks and drops that come with daily use. 
 
Tips on how to use a Bluelab Conductivity Pen to test EC in water
Start with a quality nutrient
Measuring the conductivity every day is the best way to avoid over-diluting or over-concentrating your nutrient solution
Completely change the reservoir solution every 7 days until you are confident with the nutrient
Top up the water level only between whole water changes - so your plants always have the right amount of food.
The Bluelab EC or ppm Pen also measures the temperature of the solution, as root health is vital to the success of a crop. Temperature affects the growth rate and structure of a plant so a solution temperature of 18 - 22˚C or 65 - 72˚F is recommended.