Milwaukee C65 Low Range Waterproof Conductivity Pen with ATC and Replaceable Electrode

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SKU: C65
Range: 0 to 1999 uS/cm
Resolution: 1 uS/cm
Accuracy: EC: ±2% Full Scale
Temperature Compensation: Automatic 5 to 50°C / 41 to 122°F β=2%/°C


The Milwaukee C65 Conductivity Pen is designed for aquariums, aquaculture, agriculture and pools to help you make sure that your fish or plants are receiving the right amount of nutrient to help keep your water clean and clear. Keep EC in your target range to help your achieve better results.

Design Features

  • Measures conductivity and temperature with automatic temperature compensation.
  • Ideal range for Aquaculture (0 to 1999 uS/cm).
  • Units directly in uS/cm (no conversions required). 
  • Factory calibrated with the ability to recalibrate if needed.
  • Replaceable electrode.
  • Fully waterproof to IP65.
  • 250 hours continuous use (3 x 1.5V batteries included).


Care and Use


EC electrodes can develop nutrient build up over time. To miminize build up, always rinse the probe in fresh tap or DI water after every use.

Converting EC to TDS

The Milwaukee EC Pen, like all conductivity meters, provides a measure of electrically charged ions in a solution and is an absolute measure of conductivity.

EC is often converted to TDS in parts per million (ppm). Different scales include the 500 scale, 650 scale and the 700 scale. However, true PPM can only be determined through chemical analysis.

Your uS/cm reading can be approximately converted to TDS (ppm) as shown in the examples below.

1 uS/cm = 0.5 ppm on a .5 factor scale 
1 uS/cm = 0.7 ppm on a .70 factor scale (442)


Thank you for considering Milwaukee to help you take your results to the next level.

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  • Range: 0 to 1999 uS/cm
  • Resolution: 1 uS/cm
  • Accuracy: ±2% Full Scale
  • Typical EMC Deviation: ±2% Full Scale
  • Temperature Compensation: Automatic from 5 to 50°C (41 to 122°F), with ß=2%/°C
  • Calibration: Manual, at 1 point through trimmer
  • Probe: MA73075 (replaceable)
  • Environment: 0 to 50°C / 32 to 122°F; max RH 100%
  • Battery Type: 3 x 1.5V (included)
  • Battery Life: Approx. 250 hours of continuous use
  • Dimensions: 6.5 x 1.2 x 1.2 inches (165 x 30 x 30 mm)
  • Weight: 3.5 ounces (0.99 g)