The AC Infinity pH Meter PRO Kit is a pH pen built for daily testing: a lithium glass membrane probe reading pH to ±0.01 plus temperature, sealed to IP67, with an interchangeable probe so the part that wears out can be replaced without replacing the meter. The kit comes with 4.00, 7.00 and 10.01 calibration solutions and KCL storage solution. Genuine AC Infinity, stocked in Sydney and shipped domestically.
Lab-grade precision
The probe uses a responsive lithium glass membrane that settles to a reading in seconds, and the pen reads water temperature at the same time, since pH shifts with temperature. At ±0.01 it shows small movements early: the slow upward drift of a reservoir between mixes, or how far an adjustment actually moved the number. The backlit screen shows pH and temperature together, and the pen switches itself off after 8 minutes of inactivity.
Calibration is 1, 2 or 3 point. The three solutions in the box cover all three, and the KCL solution goes in the cap to keep the glass wet in storage, which is what keeps a pH probe alive.
Replaceable design
Every pH probe wears out; AC Infinity put the average life at about 18 months. On most pens that means a new meter. On the PRO the probe unscrews from the body and a replacement probe (AC-PPA5) screws in with a sealed fit, so the pen, its screen and electronics keep working. If you test every day, that is where the PRO pays back its price over the standard kit.
Where it gets used
Nutrient reservoirs and run-off in hydroponics and coco, soil-grown feed water, and outside the grow space: aquariums and ponds, pools and spas, rainwater tanks and home brewing. IP67 means a drop into the sample is a rinse, not a replacement.
Which AC Infinity pen?
| pH Meter Kit | pH Meter PRO Kit | Hydroponic Meter PRO Kit | |
|---|---|---|---|
| Model | AC-PHM3 | AC-PHM5 | AC-PHM7 |
| Reads | pH, temp | pH, temp | pH, EC, TDS, salinity, temp |
| pH accuracy | ±0.1 | ±0.01 | ±0.01 |
| Probe | Fixed | Interchangeable | Interchangeable |
Testing occasionally? The pH Meter Kit does the job. Want EC and TDS from the same pen? That is the Hydroponic Meter PRO Kit.
Specifications
| Product identification | |
| Manufacturer | AC Infinity Inc. |
| Product name | pH Meter PRO Kit |
| Model | AC-PHM5 |
| UPC | 819137023987 |
| Performance and technical | |
| Sensor | pH and temperature |
| Probe | Interchangeable lithium glass membrane, with sensor shield |
| Accuracy | ±0.01 pH |
| Calibration | 1, 2 or 3 point (7.00 / 4.00 / 10.01) |
| Included solutions | 4.00 pH, 7.00 pH, 10.01 pH, KCL storage (use-by April 2026, see note above) |
| Ingress rating | IP67 |
| Auto off | After 8 minutes of inactivity |
| Dimensions | 4.2 × 3.3 × 17.8 cm (1.65 × 1.30 × 7.01 in) |
| Replacement probe | AC-PPA5 |
| Documentation | |
| User manual | pH Meter PRO manual (PDF) |
| Calibration | Calibration instructions (PDF) |
| Warranty | 6 months on the meter, from date of purchase. Calibration and storage solutions are consumables and are not covered. |
FAQ
Is the PRO worth it over the standard pH Meter Kit?
If you test daily, yes: ±0.01 instead of ±0.1, a 10.01 buffer for 3-point calibration, KCL storage solution, and a probe you can replace on its own. If you test once a week, the standard kit is enough.
Does it read EC or PPM?
No, pH and temperature only. For EC, TDS and salinity in the same pen, choose the Hydroponic Meter PRO Kit.
Is the included solution OK to use?
It is past its April 2026 use-by date, which is why the kit is reduced. For readings you rely on, calibrate with fresh 4.00, 7.00 and 10.01 buffer. Solutions are consumables, inexpensive and easy to buy, and are not covered by the meter's warranty.
How do I know the probe needs replacing?
Slow readings that keep creeping, or a calibration that fails or will not hold, after the probe has been cleaned and soaked in storage solution. At that point fit an AC-PPA5 replacement probe and recalibrate.
Can the Hydroponic Meter PRO probe fit this pen?
The two PRO pens take their own probes: AC-PPA5 for this pH Meter PRO, AC-PPA7 for the Hydroponic Meter PRO. Order the one that matches your pen.
How should I store it?
Wet. A few drops of KCL storage solution (or 4.00 buffer) in the cap, cap on, rinse with clean water before the next reading. Never wipe the glass bulb.