Milwaukee C66 waterproof pocket EC tester

Waterproof EC meter with a replaceable electrode, built for hydroponics and agriculture. Resolution 0.01 mS/cm.

The Milwaukee C66 reads 0.00 to 10.00 mS/cm at ± 2% of full scale, with automatic temperature compensation from 5 to 50 °C. The housing is IP65, and both the electrode and the batteries are separately replaceable. It comes with buffer sachets and a calibration screwdriver.

Replaceable parts on an inexpensive meter

On an instrument at this price a replaceable electrode looks like a detail. Over time it is the most important difference between two meters that otherwise look identical.

A conductivity sensor is robust (far more so than a pH probe) but it is not immortal. What eventually gets it is fouling that will not come off, scale that sets into the surface, or simply damage: a dropped meter, a kinked cable, a corroded contact.

At that moment two paths separate:

• Fixed electrode: you throw away a working meter because one part is finished.
• Replaceable electrode: you screw on a new one, recalibrate, and carry on.

On this meter the modular design extends to the batteries, which is the same principle: parts that wear should come out without tools or a service visit.

That also makes it a sensible choice for an environment where things get broken. In a grow room, or on a site where several people share one meter, the question is not whether something gets damaged but when, and whether that is the end of the meter.

Technical Specifications:

• EC range: 0.00 to 10.00 mS/cm
• Resolution: 0.01 mS/cm
• Accuracy: ± 2% of full scale
• Calibration: manual, 1 point via trimmer
• Temperature compensation: automatic, 5 to 50 °C (β = 2%/°C)
• Electrode: MA73076 conductivity electrode, replaceable
• Housing: IP65 waterproof, modular design
• Environment: -5 to 50 °C, max. 100% relative humidity
• Battery: 3 x 1.5 V (included), approx. 250 hours continuous use
• Dimensions: 165 x 30 x 30 mm
• weight: 80 g
• Supplied with: buffer sachets (M10031) and screwdriver

Frequently asked questions

How do I know the electrode needs replacing?
When it will no longer calibrate, when the reading keeps creeping, or when two readings moments apart differ noticeably, and cleaning has not fixed it.

Does it measure pH?
No, this is an EC meter. For acidity you need a separate meter; you need both values to steer properly.

What does IP65 mean here?
Fully dust-tight and protected against water jets. Not intended for submersion, but ample for the damp conditions of a grow room.

How often should I calibrate?
Monthly is a good rhythm, and always after cleaning the electrode.