Keep three important water parameters visible 24 hours a day, 7 days a week with the Milwaukee MC811US MAX pH/EC/Temperature Monitor.

Designed for continuous monitoring, the MC811US simultaneously displays pH, electrical conductivity (EC), and temperature across three large backlit digital displays. Once installed and calibrated, you can see current readings at a glance without repeatedly pulling out individual handheld meters.

For aquarium use, it provides a convenient way to continuously monitor pH and temperature alongside conductivity, while also being suitable for aquaculture, hydroponics, nutrient reservoirs, and other water-quality applications. Milwaukee specifically lists aquariums among the MC811's common uses.

Three Parameters. One Monitor.

Instead of using separate instruments for each measurement, the MC811US combines three monitoring functions into a single compact unit.

Continuous pH Monitoring

The included laboratory-grade MA911B/2 double-junction pH electrode continuously measures pH and connects to the monitor using a BNC connection.

Range: 0.0–12.0 pH
Resolution: 0.1 pH
Accuracy: ±0.2 pH
Calibration: Manual 2-point calibration

Electrical Conductivity Monitoring

The MC811US continuously measures electrical conductivity (EC) using its included fixed MA812 probe.

Range: 0.00–5.00 mS/cm
Resolution: 0.01 mS/cm
Accuracy: ±2% Full Scale
Calibration: Manual 1-point calibration

Temperature Monitoring

A dedicated stainless-steel temperature probe provides continuous temperature measurement.

Range: 14.0–140.0°F / -10.0–60.0°C
Resolution: 0.1°F / 0.1°C
Accuracy: ±0.5°F / ±0.3°C

Temperature is factory calibrated, and the unit provides automatic temperature compensation from 41–122°F / 5–50°C for EC measurements.

Large Backlit Displays

All three parameters are displayed simultaneously on dedicated backlit LCD readouts, making it easy to check system conditions at a glance.

That's especially convenient for systems where you want ongoing visibility instead of performing individual spot tests throughout the day.

Designed for Continuous Monitoring

Once the probes are positioned and the instrument is calibrated, the MC811US is designed to remain in operation for continuous 24/7 monitoring.

The compact monitor can be mounted above the system being tested or placed on a nearby flat surface, and its approximately 6.5-foot probe cables provide flexibility when positioning the display and probes.

Ideal For

The MC811US is suitable for applications including aquariums, aquaculture systems, hydroponics, nutrient reservoirs and other systems requiring ongoing water-quality monitoring.

For marine aquarium owners, it's important to note that EC is a conductivity measurement and should not be presented as a direct replacement for a seawater salinity or specific-gravity instrument such as the Milwaukee MA887.

Included Equipment

The MC811US includes the MA911B/2 pH electrode, fixed MA812 EC probe, fixed stainless-steel temperature probe, two probe mounting kits and 12V DC power adapter.

Additional Specifications

Model: MC811US
Dimensions: 6.3 × 4.3 × 1.4 inches
Weight: Approximately 1.2 lb
Power: Included 12V DC adapter
pH Calibration: Manual, 2 point
EC Calibration: Manual, 1 point
Temperature Calibration: Factory calibrated

Milwaukee MC811US specifications and instructions

Probe Care & Calibration

Proper probe maintenance is essential for reliable long-term monitoring.

The pH electrode should remain hydrated and should never be stored in distilled, DI, or RO water. Milwaukee recommends appropriate electrode storage solution for long-term storage and periodic cleaning and calibration as the probe ages.

EC calibration should also be performed according to Milwaukee's instructions using the appropriate calibration solution.

Monitor vs. Controller

The MC811US is designed for continuous monitoring.

It displays your current pH, EC and temperature readings but should not be confused with Milwaukee's controller products that can automatically switch external equipment or activate dosing systems.

For aquarists who want to see their parameters continuously without building out a larger aquarium controller system, that's exactly where the MC811US fits.

Why Buy From Infinity and Beyond Aquatics?

Infinity and Beyond Aquatics carries monitoring and testing equipment for aquarists who want a clearer picture of what's happening inside their systems.

The Milwaukee MC811US MAX combines three continuously displayed measurements with dedicated probes and straightforward operation, making it a powerful monitoring option for serious aquarium and water-quality applications.