EC, mS/cm, µS/cm and ppm: compare readings correctly
Different numbers can describe the same conductivity. Check the unit first and, for ppm, the conversion scale. This helps you compare meters and feeding schedules without conversion errors.
EC measures electrical conductivity
An EC meter measures how well the solution conducts electricity. Dissolved ions contribute to the result. It does not separately analyse nitrogen, phosphorus or other nutrients. Measure the source water too: some conductivity is already present before you add nutrients.
mS/cm and µS/cm differ by a factor of 1000
1 mS/cm equals 1000 µS/cm. A reading of 1.413 mS/cm therefore equals 1413 µS/cm. Check the unit on the display, reference bottle and feeding schedule. A bottle marked EC 1413 calls for checking the complete unit.
ppm depends on the conversion factor
An EC meter with a ppm display converts conductivity. On the 500 scale, 1.4 mS/cm gives 700 ppm; on the 700 scale it gives 980 ppm. This difference does not automatically mean that one solution is stronger. Check the scale on your meter and in the schedule you use.
Choose the right reference for your model
Our range includes EC 1413 and Bluelab EC 2.77. They are different reference values. Check value, unit and your meter’s procedure. Not every EC meter requires the same calibration step: a Bluelab Truncheon needs no calibration, while checks and cleaning still matter.
Compare the same measurement method
Use the same medium, sample preparation and comparable temperature. Direct substrate measurements and readings in nutrient solution or runoff are not identical tests. Record whether temperature compensation is active and how the meter presents the value. Do not compare isolated numbers without this context.
Record a short but complete measurement entry
Record date, medium, unit, value, temperature and meter or electrode model. Include the scale for ppm. Note any change in sample preparation or meter settings. Consistent records help you assess trends and check specific causes before changing the dose.
Choose your next step
Measuring & calibration for your grow room · EC meters · pH & EC meters · Calibration solutions · Bluelab meters
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