How do I convert my readings from TDS to EC and vice versa?
To get the approximate TDS value, simply multiply the EC reading (in miliSiemens/cm) by 1000 and divide by 2. To get an EC value, multiply the ppm reading by 2 and divide by 1000.
For example if your EC is 1:
1 x 1000/2 = 500ppm
And if your ppm is 500:
500 x 2/1000 = 1EC
What is the best way to measure the amount of nutrients in a solution?
In Europe, EC has been used exclusively. In the US, most growers have been using TDS. The problem is that, as explained earlier, TDS is a conversion from EC, and different manufacturers use different conversion rates. Different TDS meters may show a discrepancy of as much as 600 ppm when reading the same solution. A few years ago, at the Hydroponic Merchants' Association conference it was decided that the US industry would begin to switch over to EC. This switch over could take years.
American growers still seem to want to use TDS meters most often and we supply a wide range of quality ones. Be sure when calibrating these meters to use the correct calibrating solution from the correct manufacturer.
What nutrient level should my nutrient be at?
For seedlings, your nutrient level should be between 400ppm (800ms) and 600ppm (1,200ms). For vegetative growth, the level should be between 800ppm (1,600ms) and 1,100ppm (2,200ms). For bloom, the level should be between 1,000 ppm (2,000ms) and 1,400ppm (2,800ms). These of course are very general levels.