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Milwaukee MW500 PRO ORP Meter

$139.95 USD


  • The Milwaukee MW500 PRO ORP meter is one of Milwaukee's most popular meters with its reliable, fast, and simple operation as well as its accuracy.
  • The Milwaukee PRO ORP Meter is preferred by people looking to dial in their testing program when they have an ongoing need to maintain levels. Common uses are aquariums, swimming pools and spas, and other water quality monitoring uses.
  • The PRO ORP meter can also be used to measure sulfur dioxide in wine using the manual Ripper titration method.

What can the MILWAUKEE MW500 PRO ORP METER offer?


The PRO ORP meter is accurate to ±5 mV exceeding the needs of most users


The rugged meter is designed to take knocks.

  • The PRO ORP Meter comes with SE300 ORP probe that is both low maintenance (gel-filled) and able to withstand more challenging samples (double junction).
  • Fast easy to read current results with large digital LCD readout
  • Accurate to ±5 mV
  • Gel-filled, double junction lab grade Platinum ORP electrode for low maintenance and high performance
  • 3 feet probe cable for extra flexibility when testing
  • Auto shut off and low power demand for 300-hour extended battery life (battery included)

Use and Care

  • Properly maintaining your ORP probe will give you fast, accurate results for longer.
  • Here are our top three tips. 
  1. Always store with the cap full of buffer or storage solution, not water.
  2. Clean your probe regularly by soaking it in the cleaning solution.
  3. Calibrate after cleaning and/or storage before testing to adjust for changes in the ORP probe sensor.

How do I Calibrate?

  • The MW500 units come factory calibrated to read positive ORP. If you are looking to measure negative ORP readings, the best method is to let the probe tip sit in a small  cup or jar of white distilled vinegar for a minimum of 4 to 5 days. This allows time for the tip to oxidize and read negative ORP appropriately. When the probe is not in use, the probe needs to be stored back in the white distilled vinegar.