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What Is A Hydroponic EC Meter And How to Use It

EC meter … CF meter … truncheon meter … What are they? They are all different names for the same device! A hydroponic EC meter is a long cylinder with a sensor on the end which reads how strong your nutrient solution is. The tube has calibrated scales built-in on the sides. A red bulb lights up so you can easily catch the reading.

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hydroponic nutrient meter

Fine Tune Your Garden With A Hydroponic EC Meter

What does the EC meter do?

It determines the total amount of nutrient salts dissolved in the water. It cannot read or report anything about the individual nutrient components, only the total amount of all nutes in your solution.

Why is that important?

Different crops require different strengths of nutrient solution in order to thrive. By taking regular readings with your truncheon meter, you can fine tune your operation and stay on top of the solution long before it gets out of the desired range.

Want your hydro garden to be a class operation? Then a meter is for you.

Commercial hydroponic greenhouses use EC meters inline with their nutrient systems: it’s usually automated to adjust the solution as needed.

Don’t let the multiple names of readings confuse you, as this is not a complicated process at all. The 3 scales on the sides of a truncheon meter all line up relative to scale. You just choose which of the three units you prefer to use and stick with it.

Some folks prefer the EC, some CF, and others ppm. We prefer to use ppm, as it seems most US users do.

These are the 3 different scales which wrap around our truncheon meter: (ignore the EC x 500 scale, our chart is set up for the EC x 700 scale)

truncheon meter scales

Electronic cf units exist which are smaller, more compact. We’ve just had poor luck with electronic readout devices (unreliable) and love the truncheon type meter, so we’ll stick with that.

Now, for a little… terminology

EC = Electrical Conductivity (the measure of total dissolved solids in a solution)

CF = Conductive Factor (ditto)

ppm = Parts Per Million (same)

TDS = Total Dissolved Solids (read in ppm)

Truncheon = a baton shaped EC meter

See how we simplified all that;)

EC meter operating tips

Use and maintenance of an EC meter:

  • Follow the directions that come with the unit.
  • Clean the probe tip after each use with fresh water and dry with a soft cloth.
  • Periodically deep-clean the probe tip with rubbing alcohol. Dip briefly then rinse well with clean water. Dry with tissue or soft cloth.
  • Before long-term storage, remove the batteries.
  • How to take nutrient readings: Remove protective cap and dip probe tip into the reservoir. Hold in place for 1-2 minutes until it reaches the same temperature, then take your readings.
  • It’s a snap! You’ll wonder how you did without one.

Preferred nutrient concentrations for crops

freshly picked tomatoes, cucumbers and herbs

Below we present a chart with the preferred ranges of nutrient strength for different crops.

I know what you’re thinking… How can I grow different plants using the same reservoir if they require different nutrient solutions?

The answer is, pretty much the same way you did before you bought this gadget. Then you just relied on the bottle directions. Now, use the chart below for what you’ll be growing and average them. Find a happy middle range, test often, and you should do just fine. 

Having an EC meter is most valuable for identifying danger zones with your nutrients early on. Although not an absolute necessity, we are certainly glad we bought one; it has been an eye-opener.

Okay, here we go:

Preferred nutrient concentrations for specific plants

nutrient concentration chart


Then forget the chart. Here’s a good general guide for a hydroponic garden with mixed plants:

  • Lettuces and herbs should be grown separately, like in a lettuce raft or dedicated herb unit. Go with [0.5-1.5 EC/ 5-15 CF/ 300-1000 ppm]
  • Most other veggies: [1.4-2.4 EC/ 14-24 CF/ 980-1680 ppm]
  • Tomatoes, the heaviest feeders of all: [2.2-2.8 EC/ 22-28 CF/ 1500-1960] 
  • DANGER ZONE: Greater than 3.0 EC / 30 CF / 2000 ppm will burn your plants

Well, we certainly hope this section has helped you understand the benefits of using an EC meter. We have found ours very helpful for troubleshooting and staying one step ahead with our nutrient solution.

Want the Blue labs EC truncheon? We loved ours!

Bluelab TRUNVCOM2 Commercial Truncheon Nutrient Meter, Conductivity Measure in Solution, Increased Measurement Range
What is a hydroponic EC meter
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Stella and Simon, a couple of back-to-the-land, baby boomer enthusiasts, have embraced the world of homemade hydroponics on their three-acre plot of Florida piney woods. Their journey began after drawing inspiration from Epcot Center’s hydroponics exhibit, and they've delved into various hydroponic methods, experimenting with different systems, configurations, and crops both indoors and outdoors. Their expertise culminated in the creation of an innovative homemade hydroponics greenhouse, documented in their book, Simon’s Super Simple On-the-Grid, Off-the-Grid Hydroponic/Aquaponic Survival Greenhouse.

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