Check the listing for details. Milwaukee CD611 Digital Conductivity Pen (EC) for Hydroponics. Condition: New. Listed at 29.99 USD. DIGITAL. SIMPLE. COMPACT.The Milwaukee Conductivity Pen is designed for hydroponic and other growers to help you make sure that your plants are receiving the right amount of nutrient. Keep EC in your target range to help your achieve better results.DESIGN FEATURESMeasures conductivity and temperature with automatic temperature compensationIdeal range for hydroponics (0 to 20,000 µS/cm)Units in µS/cm easily convertable to ppmFactory calibrated with the ability to recalibrate if needed350 hours continuous use (3 x 1.5V batteries included)WHAT PEOPLE ARE SAYING Easy to Use and Carry!Works Great. I would buy again!CARE AND USEMAINTENANCEEC electrodes can develop nutrient build up over time. To miminize build up, always rinse the probe in fresh tap water after every use.CONVERTING EC TO TDSThe 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 mS/cm reading can be approximately converted to TDS (ppm) as shown in the examples below.2,000 µS/cm = 2.0 mS/cm = 1000 ppm on .50 factor scale2,000 µS/cm = 2.0 mS/cm = 1400 ppm on the 442 scale or .70 factor scale src="https://api.ucalc.pro/api/222669?bg_color=transparent&TID=S1FdXkRT#https%3A%2F%2Fmilwaukeeinstruments.com%2Fmilwaukee-cd611-digital-conductivity-pen-ec-%2F" data-mce-fragment="1" data-sanitized-data-mce-fragment="1" data-mce-src="https://api.ucalc.pro/api/222669?bg_color=transparent&TID=S1FdXkRT#https%3A%2F%2Fmilwaukeeinstruments.com%2Fmilwaukee-cd611-digital-conductivity-pen-ec-%2F" data-sanitized-data-mce-src="https://api.ucalc.pro/api/222669?bg_color=transparent&TID=S1FdXkRT#https%3A%2F%2Fmilwaukeeinstruments.com%2Fmilwaukee-cd611-digital-conductivity-pen-ec-%2F" data-sanitized-scrolling="no" data-sanitized-frameborder="0">SPECIFICATIONSRange: 0 to 20000 µS/cmResolution: 100 µS/cmAccuracy: ±2% Full ScaleTemperature Compensation: Automatic from 5 to 50°C, with ß=2%/°CCalibration: Manual, at 1 point through trimmerEnvironment: 0 to 50°C / 32 to 122°F; max RH 100%Battery Type: 4 x 1.5V Alkaline (included)Battery Life: Approx. 350 hours of continuous useDimensions: 6 x 1.2 x 0.95 inchesWeight: 3 ounces