Milwaukee PH55 PH/temp meter

Pocket meter showing pH and temperature at once, calibrating automatically, and fully waterproof. With a replaceable electrode.

The Milwaukee pH55 has an unusually wide range of -2.0 to 16.0 pH and also reads temperature from -5 to 60 °C. The large display shows both at the same time. A stability indicator shows when a reading has settled, and the hold function freezes a value so you can read it comfortably.

Automatic calibration, and which buffer you need

With manual calibration you turn a trimmer with a screwdriver until the display shows the right value. With automatic calibration the meter recognises which buffer it is sitting in and adjusts itself. All you do is hold the tip in it.

That saves more than fiddling: it removes a source of error. Adjusting by hand while the reading has not yet settled is one of the most commonly made mistakes, and it puts your meter out rather than right.

What you do need to know: there are two different buffer series, and they are not interchangeable.

• 4.01 / 7.01 / 10.01: the series you will almost always meet in horticulture.
• 4.01 / 6.86 / 9.18: the NIST series, more common in laboratories.

This meter knows both and recognises automatically which you are using. Just do not mix them within one calibration: if you start with 7.01, calibrate the second point with 4.01 and not with 6.86.

The pH55 calibrates at one or two points. Two is advisable as soon as you want to steer precisely, for the same reason as on any two-point meter: you then correct not only the zero point but the slope.

Technical Specifications:

• pH range: -2.0 to 16.0 pH
• resolution: 0.1 pH
• accuracy: ± 0.1 pH
• Temperature range: -5.0 to 60.0 °C
• accuracy: ± 0.5 °C
• Calibration: automatic, 1 or 2 points, two buffer sets in memory
• Temperature compensation: automatic, -5 to 60 °C
• Electrode: Mi56P, replaceable
• Housing: IP67 waterproof
• Battery: 4 x 1.5 V, IEC LR44 / A76 (included), approx. 300 hours
• Auto shut-off: after 8 minutes
• Dimensions: 200 x Ø 38 mm
• weight: 100 g
• Supplied with: protective cap, pH 4.01 and 7.01 buffer sachets, batteries, instructions

Frequently asked questions

What is the difference from the pH51?
The pH55 calibrates automatically rather than manually, reads temperature with automatic compensation, and is IP67 rather than IP65. The pH51 is simpler and cheaper.

What would I need a range up to 16 pH for?
For growing, nothing. It exists for applications outside horticulture. What matters to you is that the meter is accurate within your working range.

What does the stability indicator do?
It shows when a reading has settled. A pH reading still creeps for the first few seconds; reading it too early is a classic mistake.

IP67: can it go underwater?
IP67 covers temporary submersion. It is not intended, but it will survive falling into your reservoir.