The AC Infinity pH Meter Kit is a pocket pH pen for water — a lithium glass membrane probe reading pH and temperature to ±0.1, sealed to IP67 so a drop in the reservoir does not end it. Calibration solutions and a sensor shield are in the box. Genuine AC Infinity, stocked in Sydney and shipped domestically.
Reduced price — please read before ordering. The calibration solutions supplied with this kit carry a use-by date of April 2026, which has now passed. Sealed buffer solution degrades slowly rather than suddenly, but we will not tell you it is still accurate, so the price is reduced accordingly. Calibrate with fresh 4.00 and 7.00 solution if the reading matters. Calibration solutions are consumables and are not covered by warranty; replacements are inexpensive and easy to find. The meter itself is new, unused and covered by our 6-month warranty.
What it actually measures, and why it matters
pH controls which nutrients a root system can take up. Get it wrong and a feed chart that should work stops working — the nutrients are in the water but locked out of the plant. That is why nutrient deficiency symptoms so often turn out to be a pH problem rather than a feeding problem, and why a $65 pen saves more than it costs.
This meter reads pH and water temperature together, which matters because pH readings shift with temperature. The probe uses a lithium glass membrane — the standard for a responsive electrode — and settles to a reading in seconds rather than drifting for a minute.
It is not only a hydroponics tool
The same pen works on anything you need a pH figure for: reservoirs and run-off, pond and aquarium water, pool and spa water, rainwater tanks, home brewing, and water treatment generally. IP67 means it is sealed against dust and against immersion, so dropping it into what you are testing is an inconvenience rather than a replacement.
Between uses the probe sits inside a sensor shield. That is not packaging — a glass electrode left to dry out is the single most common way these pens die. Keep the cap on and a few drops of storage or 4.00 solution in it.
This kit or the pH Meter PRO?
| pH Meter Kit | pH Meter PRO Kit | |
|---|---|---|
| Model | AC-PHM3 | AC-PHM5 |
| Probe | Fixed, lithium glass membrane | Interchangeable — replace the probe, keep the pen |
| Accuracy | ±0.1 pH | ±0.01 pH |
| Best for | Occasional checks, a single reservoir, general water testing | Daily use, where the probe is a wear item you will replace |
The probe is the part that wears out on any pH pen; AC Infinity put the average life at about 18 months. If you will be testing every day, the pH Meter PRO Kit works out cheaper over time because you replace a probe instead of a whole meter. If you test occasionally, this kit is the right buy.
Specifications
| Manufacturer | AC Infinity Inc. |
| Model | AC-PHM3 |
| UPC | 819137024205 |
| Sensor | pH and temperature |
| Probe | Lithium glass membrane, fixed, with sensor shield |
| Accuracy | ±0.1 pH |
| Included solutions | 4.00 pH and 7.00 pH buffers (use-by April 2026 — see note above) |
| Ingress rating | IP67 |
| Dimensions | 4.2 × 3.0 × 17.8 cm (1.65 × 1.18 × 7.01 in) |
| Manual | pH Meter user manual (PDF) |
| Calibration | Calibration instructions (PDF) |
| Warranty | 6 months on the meter, from date of purchase. Calibration solutions are consumables and are not covered. |
Questions we get asked
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 and 7.00 buffer. Solutions are consumables, inexpensive and easy to buy, and are not covered by the meter's warranty.
How often do I need to calibrate it?
Monthly for regular use, and always after storing it dry, after a knock, or whenever a reading looks wrong. Two-point calibration with 7.00 first and then 4.00 takes under a minute and is the difference between a meter you can trust and a number on a screen.
Why does my reading drift?
Three usual causes, in order: the probe has dried out, the calibration is stale, or the water temperature has changed between readings. Rinse with plain water between samples, never wipe the glass, and store the probe wet.
Does it read EC or PPM as well?
No. This is pH and temperature only. EC and PPM need a separate conductivity meter such as the AZ 8362 EC & TDS Pen, or the Hydroponic Meter PRO Kit for both in one pen.
Can I replace the probe when it wears out?
Not on this model — the probe is fixed. If you want a replaceable probe, that is the reason the pH Meter PRO Kit exists.
Can I use it in a pool, spa or aquarium?
Yes. It is a general-purpose water pH pen. Rinse it after anything salty or heavily chlorinated, because salt left on a glass electrode shortens its life.
Is this genuine stock with an Australian warranty?
Yes. Quick Bloom Lights is the official Australian importer and distributor for AC Infinity. Stock is held in Sydney and warranty is handled here rather than through an overseas seller.