Handy 20ml sachets of 1413 solution to calibrate your digital EC meter.
Get used to maintaining these meters, as calibrated in this way you ensure an accurate EC measurement of your nutrient solution. You will always be able to give your plants the necessary nutrients at each stage of the plant's cycle without making any mistakes.
Just dip the electrode in the sachet and wait a few seconds, then you can make a mark on the EC meter in an easy and reliable way.