Apera PH20
#9 in Pen testersFull review
A cheap, waterproof pen for pools, aquariums and drinking water. Pick it when 0.1 pH is close enough.
Amazon $56.65$56.65
The Apera PH20 is the better ph meter overall, rated 3.1 to 3.0. The Apera PH20 leads on calibration and price. The Milwaukee pH55 Pro wins on features. The Apera PH20 costs $21.25 less ($56.65 vs $77.90).
Prices were last checked November 9, 2026. Product prices and availability are accurate as of that date and are subject to change; the price and availability shown on Amazon or the retailer's site at the time of purchase apply. As an Amazon Associate we earn from qualifying purchases.
Milwaukee pH55 Pro
#11 in Pen testersFull review
A low-cost pen with a replaceable electrode, for pools, gardens and aquariums. The Apera PH60 is more accurate for a little more.
Amazon $77.90$77.90
Which should you buy?
- Choose the Apera PH20 for calibration (3-point calibration vs 2-point calibration) and price ($56.65 vs $77.90).
- Choose the Milwaukee pH55 Pro for features (replaceable probe, automatic temperature compensation, waterproof (IP65) vs automatic temperature compensation, waterproof (IP67)).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every pen testers ph meter; a clear win is highlighted. How we rank explains each one.
| Factor weight | Apera PH20 | Milwaukee pH55 Pro |
|---|---|---|
| Overall rating | 3.1/5 | 3.0/5 |
| Accuracy 30% | 19 ±0.1 pH | 19 ±0.1 pH |
| Calibration 15% | 85 3-point calibration | 50 2-point calibration |
| Features 20% | 50 automatic temperature compensation, waterproof (IP67) | 70 replaceable probe, automatic temperature compensation, waterproof (IP65) |
| Extra readings 10% | 0 pH and temperature only | 0 pH and temperature only |
| Price 15% | 100 $56.65 | 89 $77.90 |
| Warranty 10% | 25 2-year meter warranty | 25 2-year meter warranty |
Specifications
| Apera PH20 | Milwaukee pH55 Pro | |
|---|---|---|
| pH measurement | ||
| Accuracy | ±0.1 pH | ±0.1 pH |
| Resolution | 0.1 pH | 0.1 pH |
| Range | 0 to 14 pH | -2 to 16 pH |
| Calibration | 3-point | 2-point |
| Temperature compensation | Yes | Yes |
| Other readings | ||
| Conductivity (EC/TDS) | No | No |
| ORP | No | No |
| Salinity | No | No |
| Build | ||
| Replaceable probe | No | Yes |
| Waterproof rating | IP67 | IP65 |
| Battery life | 2,000 hours | 300 hours |
| Weight | 107 g | 99 g |
| Meter warranty | 2 years | 2 years |
| Probe warranty | 6 months | 6 months |