Bluelab Truncheon EC meter standard 0.2 - 3.6

No buttons, no screen, no calibration. You put it in your reservoir and a row of blue LEDs tells you the strength of your solution. Five-year warranty.

The Bluelab Truncheon standard reads 0.2 to 3.6 EC at an accuracy of ± 4%. It is 40.7 centimetres long, fully waterproof, switches itself on and off, and runs on three AA batteries. There is not a single button on it.

Why this meter never needs calibrating

This is the feature the Truncheon's reputation rests on, and it deserves explaining, because "needs no calibration" sounds like a marketing claim and is not one.

On a pH meter, calibration is unavoidable. The glass membrane ages, and the relationship between the voltage it produces and acidity slowly shifts. Without regular adjustment such a meter drifts away without showing you.

A conductivity sensor works quite differently. It measures a physical property of the water between two fixed electrodes. No membrane to age, no reference solution to contaminate. The distance between those electrodes does not change, so the measurement does not either.

That is why the Truncheon is factory set and stays that way. You can check it against an EC 2.77 solution if you want reassurance, but adjusting it is neither necessary nor possible.

What does matter is keeping it clean. Salt build-up on the electrodes is the only thing that puts this meter off course. Rinsing after use and cleaning periodically is the entire maintenance, and they last years on that: hence the five-year warranty.

Four scales on one meter

Four scales run side by side along the body, and that solves the most confusing problem in measuring feed in one go.

• EC: the actual measurement, in mS/cm.
• CF: simply EC times ten. EC 2.0 is CF 20.
• ppm 500: EC converted using a factor of 0.5.
• ppm 700: EC converted using a factor of 0.7.

That there are two ppm scales is exactly what trips growers up: the same water is 1000 ppm on one and 1400 ppm on the other. If you follow a feed schedule in ppm, you can read the matching value straight off here instead of working out which scale the author meant.

Technical Specifications:

• EC range: 0.2 to 3.6 EC
• Resolution: 0.1 EC
• accuracy: ± 4%
• Scales: EC, CF, ppm 500 and ppm 700
• Calibration: not required and not possible; checkable against EC 2.77
• Display: blue LEDs, readable in daylight
• Controls: none, switches on and off automatically
• Length: 40.7 cm
• build: fully waterproof
• Battery: 3 x AA (included)
• Warranty: 5 years

Frequently asked questions

Which range do I need: this or the commercial?
This standard version covers 0.2 to 3.6 EC, which is where almost all indoor growing sits. The commercial goes to 6.0 and is meant for stronger solutions.

Isn't ± 4% imprecise?
At EC 2.0 that is about 0.08: smaller than the steps you steer in. What matters more is that the reading stays stable, and it does, year after year.

Does it show temperature?
It compensates for it but does not display it. To read water temperature, choose the Conductivity Pen or a combi meter.

Why is it so long?
So you can measure in a deep reservoir without putting your hand in the solution.

Can I use it in soil or coco?
No, it is for liquid. For the medium itself, the Bluelab Pulse is the tool.