PPM and EC figures arent matching

Indoor, LSD Fem. MH/HPS 750w , FF ocean soil and FF nutes , GB, BB , Tiger bloom nutes …Appx 54-56 days old … Just been giving them 1/2 the strength of nutes every other watering … nothing strong , and only about 2 weeks now … Just 1 fan leaf had 3 brown spots … 3 plants and just 1 leaf on the bottom of 1 plant , I chopped it off and looked on the underside , no bugs … I checked the run off on EC and PPM , but dont know a dam thing , The #'s are wayyyy off … PPM was 1684 and EC was 3368 … From the chart it doesnt make sense to me … WTF !!!

Fox farms Ppms/ec are in the .7 scale (truncheon). Your meter is likely on the .5 scale (Hanna). Here is a conversion chart.

Your 1600 ppm coming out is equivalent to fox farms 2240ppm. So your ec and ppm do line up. 1600 ppm equals 3.2 ec on the Hanna scale. What are your ppms going in?


Most normal readings are hanna.

Your meter is microsemens, that chart is millisemens. Just a decimal thing…


I have that same TDS meter.
Your readings 1600 ppm and 3200 EC (3.2) are the same relating to the particles in the water solution.
EC reading will always be double of what the PPM reading is with that meter.
EC doesn’t use mathematical conversion where PPM does convert number and your meter uses 50% conversion.
Most feed schedules refer to PPM for input so you can just leave the meter set to PPM for taking readings. Just be aware of what setting your meter is on when reading solutions. If you see a reading that doesn’t seem right check the display and make sure it is set to PPM and Fahrenheit US something or another on display.
Other meters use different % conversions as the chart above shows.
EC is always EC regardless of meter or conversion where depending on meter formula PPM can be different from meter to meter.
Crazy but that’s what they did with PPM from different manufacturers from different parts of the world.



I would just use the EC readings if your feed schedule shows that.
PPM in my opinion is a pain in the ace