Milwaukee pH51 pH Meter

Overview 

The ph51 is a low priced digital pH meter manufactured by Milwaukee Instruments.  The documentation says that it features a detection range from pH 0.0 to 14.0 (which is the entire range of possible pH's).  It measures pH by using a calibrated electrode (probe) in your solution.

From what I can tell, it's aimed at the introductory level folks who are looking to gain control of their water chemistry.  The package includes a the meter itself, protective case, instruction manual, warranty card, adjustment screwdriver, and two sample packets of pH reference solutions.

The unit is calibrated using two difference reference solutions.  Each one is set to a specific and reliable pH, so they can be used to "dial in" the device.  It requires both a pH 4.01 solition (for the acidic end of the scale) and a pH 7.01 solution (for the middle range of the scale).  The calibration itself is performed by adjusting two "trimmers" with a small screwdriver, which is included in the package.

The meter is powered by three tiny batteries (1.5V each).  The batteries are easily replaceable, as is the electrode.

You can easily access the battery compartment and calibration trimmers by removing the rear cap of the meter. Additionally, once the rear cap has been removed, you can also see the two adjustment trimmers.  These trimmers can be adjusted using the included screwdriver.

Acquisition

We purchased the pH51 meter(s) at market rate, though a normal hydroponics retailer.  Nothing was provided as an incentive to review this product. We paid about $65 for our unit.  Additionally, we received a replacement unit from Milwaukee (under warranty) as the first unit failed.

Observations

We tested two different units of the pH51 meter, over the period of a few weeks.  The unit is a convenient size, and we were glad to see a starter pack of the calibration fluids included in the package.

As recommended by the instructions, we "conditioned" the electrode of the new unit in the calibration fluid.  After conditioning the electrode, we proceeded to calibrate the unit (using the included reference solutions).

We spent quite a while calibrating the units that we tested.  We used both the 4.01 solution and the 7.01 solution.  We carefully adjusted each of the trimmers, and calibrated the meter as exactly as possible.

Although we were able to properly calibrate each unit initially, the readings we obtained from the meters were extremely erratic.  We were unable to get steady readings even in the reference solutions, just minutes after initial calibration.  Sadly, we didn't know this initially, and ruined a good number of plants when we mistakenly "trusted" the readings provided by the first meter.

Having met with puzzling defeat with our first sample meter, we contacted customer service at Milwaukee.  To Milwaukee's credit, their customer service operation was really first-rate.  They offered us advice, and failing a solution to our problem, happily replaced our meter.

Sadly, the second meter met with identical results as the first.  The results were unreliable as best, and useless at worst.  We found the meter to be significantly less reliable than even crude "color change" test kits. 

Recommendations

Although Milwaukee stood behind their product, and offered excellent customer service; we cannot recommend this product.  It's time-consuming calibration, combined with it's unreliability, makes it practically useless in any practical application.  It's a nice compact design, but just doesn't work well enough to recommend.