Milwaukee ORP57 PRO Waterproof ORP/Temperature Tester with Replaceable Probe

SKU: 9139-ORP57~ea

Milwaukee ORP57 PRO Waterproof ORP/Temperature Tester with Replaceable Probe

SKU: 9139-ORP57~ea
Regular price $205.25 CAD
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Milwaukee ORP57 PRO Waterproof ORP/Temperature Tester with Replaceable Probe

The Milwaukee ORP57 PRO ORP/Temperature Tester is designed for laboratory, pools, education, water treatment and many other applications. It is the ideal meter to help make sure that your ORP/Temperature needs are being met and that you are getting reliable results for your analysis.


  • Measures temperature and ORP with automatic temperature compensation (ATC).
  • Ideal range for pools and all different applications (+/- 1000 mV| -5.0 to 60°C (23.0 to 140.0°F). 
  • Units direct in mV.
  • Factory calibrated (no need to recalibrate).
  • Replaceable electrode Mi57P.
  • Fully waterproof to IP67
  • Approximately 300 hours of use (4 x 1.5V batteries included)


  • ORP Range: ±1000 mV (ORP)
  • Temp Range: -5 to 60.0°C / 23.0 to 140.0°F
  • ORP Resolution: 1 mV
  • Temp Resolution: 0.1°C / 0.1°F
  • ORP Accuracy: ±2 mV
  • Temp Accuracy: ±0.5°C / ±1°F
  • EC Typical EMC Deviation: ±2 mV
  • Typical EMC Deviation Temperature: ±0.3°C ±0.6°F
  • Calibration: Factory Calibrated (no additional calibration required)
  • Probe: Mi57P (replaceable)
  • Environment: -5 to 50°C / 23 to 122°F; max RH 100%
  • Battery Type: 4 x 1.5V; IEC LR44, A76 (included)
  • Battery Life: Approx. 300 hours of use
  • Auto-off: After 8 minutes of non-use
  • Dimensions: 7.9 × dia 1.5 inches
  • Weight: 3.5 ounces (99.22 g)

Milwaukee ORP57 Manual




ORP meters usually start performing poorly because of problems with the probe, either with the glass sensing bulb or the reference junction.  The glass bulb loses sensitivity with use and will eventually fail. This is true of all ORP probes.  The reference junction is a small hole that allows the meter to compare the sample to a reference. The reading is generated based on the electrical difference between the sample and reference. If the junction hole gets clogged, the ORP electrode will no longer function.


To minimize clogging, the ORP probe needs to be kept hydrated. Long periods of dry storage will damage the sensitivity of the probe. Allowing the probe to dry out may also result in the junction hole getting clogged.

Storing the ORP probe in storage solution MA9015 will help address this issue. Do not store in tap water or DI water. This will damage the sensitivity of the probe.

The best way to store the probe is with the probe's cap filled with storage solution or calibration buffer and the cap tightened to prevent leakage. It is also recommended that to store the electrode upright to further reduce the potential for leakage.


Residue from the sample can impact the sensitivity of the sensing bulb and clog the junction. This is especially true if the sample has a lot of organic material. It is recommended to regularly soak your electrode in cleaning solution MA9016. You can also:

  1. Inspect the electrode for damage or scratches. If present, replace the electrode.
  2. Inspect the cable.  The connection cable and insulation must be intact.
  3. Connectors should be clean and dry.
  4. Rinse off salt deposits with water or DI water.
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