Control Wizard EC Dipstick (previously Nutra-Wand) 

The EC Dipstick is one of the easiest meters to use, providing the 4 most popular scales: EC, CF, 500:1ppm, and 700:1ppm! 

The EC Dipstick dissolved salts pen operates on 3 common inexpensive AA alkaline batteries.Measures in PPM, EC and CF scales. No calibration required. It calibrates itself each time you replace the batteries.

The main idea behind all meters is for you to mix your plant food in your water and take a reading, then log that reading for future use.

If you want to quote numbers, look to the international EC or CF scale for your numbers (CF is 10 times EC). EC stands for electrical conductivity. Simply note where the light blinks and your done.